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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>security-guide</title><link rel="stylesheet" href="./Common_Content/css/default.css" type="text/css" /><meta name="generator" content="publican 0.60" /><meta name="package" content="fedora-security-guide-12-en-US-1.1-18" /><meta name="description" content="The Linux Security Guide is designed to assist users of Linux in learning the processes and practices of securing workstations and servers against local and remote intrusion, exploitation, and malicious activity. Focused on Fedora Linux but detailing concepts and techniques valid for all Linux systems, The Linux Security Guide details the planning and the tools involved in creating a secured computing environment for the data center, workplace, and home. With proper administrative knowledge, vigilance, and tools, systems running Linux can be both fully functional and secured from most common intrusion
and exploit methods." /></head><body class=""><div xml:lang="en-US" class="book" title="security-guide" lang="en-US"><div class="titlepage"><div><div class="producttitle"><span class="productname">fedora</span> <span class="productnumber">12</span></div><div><h1 id="id1962982" class="title">security-guide</h1></div><div><h2 class="subtitle">A Guide to Securing Fedora Linux</h2></div><p class="edition">Edition 1.1</p><div><h3 class="corpauthor">
<span class="inlinemediaobject"><object data="Common_Content/images/title_logo.svg" type="image/svg+xml"> Logo</object></span>
</h3></div><div><div xml:lang="en-US" class="authorgroup" lang="en-US"><div class="author"><h3 class="author"><span class="firstname">Johnray</span> <span class="surname">Fuller</span></h3><div class="affiliation"><span class="orgname">Red Hat</span></div><code class="email"><a class="email" href="mailto:jrfuller at redhat.com">jrfuller at redhat.com</a></code></div><div class="author"><h3 class="author"><span class="firstname">John</span> <span class="surname">Ha</span></h3><div class="affiliation"><span class="orgname">Red Hat</span></div><code class="email"><a class="email" href="mailto:jha at redhat.com">jha at redhat.com</a></code></div><div class="author"><h3 class="author"><span class="firstname">David</span> <span class="surname">O'Brien</span></h3><div class="affiliation"><span class="orgname">Red Hat</span></div><code class="email"><a class="email" href="mailto:daobrien at redhat.com">daobrien at redhat.com</a></code></div><div class="author"><h3 class="author"><span class="firstnam
e">Scott</span> <span class="surname">Radvan</span></h3><div class="affiliation"><span class="orgname">Red Hat</span></div><code class="email"><a class="email" href="mailto:sradvan at redhat.com">sradvan at redhat.com</a></code></div><div class="author"><h3 class="author"><span class="firstname">Eric</span> <span class="surname">Christensen</span></h3><div class="affiliation"><span class="orgname">Fedora Project</span> <span class="orgdiv">Documentation Team</span></div><code class="email"><a class="email" href="mailto:sparks at fedoraproject.org">sparks at fedoraproject.org</a></code></div></div></div><hr /><div><div id="id645691" class="legalnotice"><h1 class="legalnotice">Legal Notice</h1><div class="para">
Copyright <span class="trademark"></span>© 2009 Red Hat, Inc.
</div><div class="para">
The text of and illustrations in this document are licensed by Red Hat under a Creative Commons Attribution–Share Alike 3.0 Unported license ("CC-BY-SA"). An explanation of CC-BY-SA is available at <a href="http://creativecommons.org/licenses/by-sa/3.0/">http://creativecommons.org/licenses/by-sa/3.0/</a>. The original authors of this document, and Red Hat, designate the Fedora Project as the "Attribution Party" for purposes of CC-BY-SA. In accordance with CC-BY-SA, if you distribute this document or an adaptation of it, you must provide the URL for the original version.
</div><div class="para">
Red Hat, as the licensor of this document, waives the right to enforce, and agrees not to assert, Section 4d of CC-BY-SA to the fullest extent permitted by applicable law.
</div><div class="para">
Red Hat, Red Hat Enterprise Linux, the Shadowman logo, JBoss, MetaMatrix, Fedora, the Infinity Logo, and RHCE are trademarks of Red Hat, Inc., registered in the United States and other countries.
</div><div class="para">
For guidelines on the permitted uses of the Fedora trademarks, refer to <a href="https://fedoraproject.org/wiki/Legal:Trademark_guidelines">https://fedoraproject.org/wiki/Legal:Trademark_guidelines</a>.
</div><div class="para">
<span class="trademark">Linux</span>® is the registered trademark of Linus Torvalds in the United States and other countries.
</div><div class="para">
All other trademarks are the property of their respective owners.
</div></div></div><div><div class="abstract" title="Abstract"><h6>Abstract</h6><div class="para">
The Linux Security Guide is designed to assist users of Linux in
learning the processes and practices of securing workstations and
servers against local and remote intrusion, exploitation, and
malicious activity.
</div><div class="para">
Focused on Fedora Linux but detailing concepts and techniques valid
for all Linux systems, The Linux Security Guide details the
planning and the tools involved in creating a secured computing
environment for the data center, workplace, and home.
</div><div class="para">
With proper administrative knowledge, vigilance, and tools, systems
running Linux can be both fully functional and secured from most
common intrusion and exploit methods.
</div></div></div></div><hr /></div><div class="toc"><dl><dt><span class="preface"><a href="#pref-Security_Guide-Preface">Preface</a></span></dt><dd><dl><dt><span class="section"><a href="#id639409">1. Document Conventions</a></span></dt><dd><dl><dt><span class="section"><a href="#id645070">1.1. Typographic Conventions</a></span></dt><dt><span class="section"><a href="#id591154">1.2. Pull-quote Conventions</a></span></dt><dt><span class="section"><a href="#id645085">1.3. Notes and Warnings</a></span></dt></dl></dd><dt><span class="section"><a href="#We_Need_Feedback">2. We Need Feedback!</a></span></dt></dl></dd><dt><span class="chapter"><a href="#chap-Security_Guide-Security_Overview">1. Security Overview</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Introduction_to_Security">1.1. Introduction to Security</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Introduction_to_Security-What_is_Computer_Security">1.1.1. W
hat is Computer Security?</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Introduction_to_Security-SELinux">1.1.2. SELinux</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Introduction_to_Security-Security_Controls">1.1.3. Security Controls</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Introduction_to_Security-Conclusion">1.1.4. Conclusion</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-Vulnerability_Assessment">1.2. Vulnerability Assessment</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Vulnerability_Assessment-Thinking_Like_the_Enemy">1.2.1. Thinking Like the Enemy</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Vulnerability_Assessment-Defining_Assessment_and_Testing">1.2.2. Defining Assessment and Testing</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Vulnerability_Assessment-Evaluating_the_T
ools">1.2.3. Evaluating the Tools</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-Attackers_and_Vulnerabilities">1.3. Attackers and Vulnerabilities</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Attackers_and_Vulnerabilities-A_Quick_History_of_Hackers">1.3.1. A Quick History of Hackers</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Attackers_and_Vulnerabilities-Threats_to_Network_Security">1.3.2. Threats to Network Security</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Attackers_and_Vulnerabilities-Threats_to_Server_Security">1.3.3. Threats to Server Security</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Attackers_and_Vulnerabilities-Threats_to_Workstation_and_Home_PC_Security">1.3.4. Threats to Workstation and Home PC Security</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-Common_Exploits_and_Attacks">1.
4. Common Exploits and Attacks</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Security_Updates">1.5. Security Updates</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Security_Updates-Updating_Packages">1.5.1. Updating Packages</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Updating_Packages-Verifying_Signed_Packages">1.5.2. Verifying Signed Packages</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Updating_Packages-Installing_Signed_Packages">1.5.3. Installing Signed Packages</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Updating_Packages-Applying_the_Changes">1.5.4. Applying the Changes</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#chap-Security_Guide-Securing_Your_Network">2. Securing Your Network</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Workstation_Security">2.1. Workstation Security</a
></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Workstation_Security-Evaluating_Workstation_Security">2.1.1. Evaluating Workstation Security</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Workstation_Security-BIOS_and_Boot_Loader_Security">2.1.2. BIOS and Boot Loader Security</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Workstation_Security-Password_Security">2.1.3. Password Security</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Workstation_Security-Administrative_Controls">2.1.4. Administrative Controls</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Workstation_Security-Available_Network_Services">2.1.5. Available Network Services</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Workstation_Security-Personal_Firewalls">2.1.6. Personal Firewalls</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Workstation_
Security-Security_Enhanced_Communication_Tools">2.1.7. Security Enhanced Communication Tools</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-Server_Security">2.2. Server Security</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Server_Security-Securing_Services_With_TCP_Wrappers_and_xinetd">2.2.1. Securing Services With TCP Wrappers and xinetd</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Server_Security-Securing_Portmap">2.2.2. Securing Portmap</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Server_Security-Securing_NIS">2.2.3. Securing NIS</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Server_Security-Securing_NFS">2.2.4. Securing NFS</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Server_Security-Securing_the_Apache_HTTP_Server">2.2.5. Securing the Apache HTTP Server</a></span></dt><dt><span class="section"><a href="
#sect-Security_Guide-Server_Security-Securing_FTP">2.2.6. Securing FTP</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Server_Security-Securing_Sendmail">2.2.7. Securing Sendmail</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Server_Security-Verifying_Which_Ports_Are_Listening">2.2.8. Verifying Which Ports Are Listening</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-Single_Sign_on_SSO">2.3. Single Sign-on (SSO)</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Single_Sign_on_SSO-Introduction">2.3.1. Introduction</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Single_Sign_on_SSO-Getting_Started_with_your_new_Smart_Card">2.3.2. Getting Started with your new Smart Card</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Single_Sign_on_SSO-How_Smart_Card_Enrollment_Works">2.3.3. How Smart Card Enrollment Works</a></span></dt><dt>
<span class="section"><a href="#sect-Security_Guide-Single_Sign_on_SSO-How_Smart_Card_Login_Works">2.3.4. How Smart Card Login Works</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Single_Sign_on_SSO-Configuring_Firefox_to_use_Kerberos_for_SSO">2.3.5. Configuring Firefox to use Kerberos for SSO</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-Pluggable_Authentication_Modules_PAM">2.4. Pluggable Authentication Modules (PAM)</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Pluggable_Authentication_Modules_PAM-Advantages_of_PAM">2.4.1. Advantages of PAM</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Pluggable_Authentication_Modules_PAM-PAM_Configuration_Files">2.4.2. PAM Configuration Files</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Pluggable_Authentication_Modules_PAM-PAM_Configuration_File_Format">2.4.3. PAM Configuration File Format</a></sp
an></dt><dt><span class="section"><a href="#sect-Security_Guide-Pluggable_Authentication_Modules_PAM-Sample_PAM_Configuration_Files">2.4.4. Sample PAM Configuration Files</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Pluggable_Authentication_Modules_PAM-Creating_PAM_Modules">2.4.5. Creating PAM Modules</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Pluggable_Authentication_Modules_PAM-PAM_and_Administrative_Credential_Caching">2.4.6. PAM and Administrative Credential Caching</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Pluggable_Authentication_Modules_PAM-PAM_and_Device_Ownership">2.4.7. PAM and Device Ownership</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Pluggable_Authentication_Modules_PAM-Additional_Resources">2.4.8. Additional Resources</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-TCP_Wrappers_and_xinetd">2.5. TCP Wrappers and xinetd</
a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-TCP_Wrappers_and_xinetd-TCP_Wrappers">2.5.1. TCP Wrappers</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-TCP_Wrappers_and_xinetd-TCP_Wrappers_Configuration_Files">2.5.2. TCP Wrappers Configuration Files</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-TCP_Wrappers_and_xinetd-xinetd">2.5.3. xinetd</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-TCP_Wrappers_and_xinetd-xinetd_Configuration_Files">2.5.4. xinetd Configuration Files</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-TCP_Wrappers_and_xinetd-Additional_Resources">2.5.5. Additional Resources</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-Kerberos">2.6. Kerberos</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Kerberos-What_is_Kerberos">2.6.1. What is Kerberos?</a></span></dt><dt><span clas
s="section"><a href="#sect-Security_Guide-Kerberos-Kerberos_Terminology">2.6.2. Kerberos Terminology</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Kerberos-How_Kerberos_Works">2.6.3. How Kerberos Works</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Kerberos-Kerberos_and_PAM">2.6.4. Kerberos and PAM</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Kerberos-Configuring_a_Kerberos_5_Server">2.6.5. Configuring a Kerberos 5 Server</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Kerberos-Configuring_a_Kerberos_5_Client">2.6.6. Configuring a Kerberos 5 Client</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Kerberos-Domain_to_Realm_Mapping">2.6.7. Domain-to-Realm Mapping</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Kerberos-Setting_Up_Secondary_KDCs">2.6.8. Setting Up Secondary KDCs</a></span></dt><dt><span class="section"><a href="#sect-Secu
rity_Guide-Kerberos-Setting_Up_Cross_Realm_Authentication">2.6.9. Setting Up Cross Realm Authentication</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Kerberos-Additional_Resources">2.6.10. Additional Resources</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-Virtual_Private_Networks_VPNs">2.7. Virtual Private Networks (VPNs)</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Virtual_Private_Networks_VPNs-How_Does_a_VPN_Work">2.7.1. How Does a VPN Work?</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Virtual_Private_Networks_VPNs-VPNs_and_PROD">2.7.2. VPNs and Fedora</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Virtual_Private_Networks_VPNs-IPsec">2.7.3. IPsec</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Virtual_Private_Networks_VPNs-Creating_an_IPsec_Connection">2.7.4. Creating an <abbr class="abbrev">IPsec</abbr> Con
nection</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Virtual_Private_Networks_VPNs-IPsec_Installation">2.7.5. IPsec Installation</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Virtual_Private_Networks_VPNs-IPsec_Host_to_Host_Configuration">2.7.6. IPsec Host-to-Host Configuration</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Virtual_Private_Networks_VPNs-IPsec_Network_to_Network_Configuration">2.7.7. IPsec Network-to-Network Configuration</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Virtual_Private_Networks_VPNs-Starting_and_Stopping_an_IPsec_Connection">2.7.8. Starting and Stopping an <abbr class="abbrev">IPsec</abbr> Connection</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-Firewalls">2.8. Firewalls</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Firewalls-Netfilter_and_IPTables">2.8.1. Netfilter and IPTables</
a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Firewalls-Basic_Firewall_Configuration">2.8.2. Basic Firewall Configuration</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Firewalls-Using_IPTables">2.8.3. Using IPTables</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Firewalls-Common_IPTables_Filtering">2.8.4. Common IPTables Filtering</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Firewalls-FORWARD_and_NAT_Rules">2.8.5. <code class="computeroutput">FORWARD</code> and <acronym class="acronym">NAT</acronym> Rules</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Firewalls-Malicious_Software_and_Spoofed_IP_Addresses">2.8.6. Malicious Software and Spoofed IP Addresses</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Firewalls-IPTables_and_Connection_Tracking">2.8.7. IPTables and Connection Tracking</a></span></dt><dt><span class="section"><a hre
f="#sect-Security_Guide-Firewalls-IPv6">2.8.8. IPv6</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Firewalls-Additional_Resources">2.8.9. Additional Resources</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-IPTables">2.9. IPTables</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-IPTables-Packet_Filtering">2.9.1. Packet Filtering</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-IPTables-Command_Options_for_IPTables">2.9.2. Command Options for IPTables</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-IPTables-Saving_IPTables_Rules">2.9.3. Saving IPTables Rules</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-IPTables-IPTables_Control_Scripts">2.9.4. IPTables Control Scripts</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-IPTables-IPTables_and_IPv6">2.9.5. IPTables and IPv6</a></span></dt><dt><span class=
"section"><a href="#sect-Security_Guide-IPTables-Additional_Resources">2.9.6. Additional Resources</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#chap-Security_Guide-Encryption">3. Encryption</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Encryption-Data_at_Rest">3.1. Data at Rest</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Encryption-Protecting_Data_at_Rest-Full_Disk_Encryption">3.2. Full Disk Encryption</a></span></dt><dt><span class="section"><a href="#Security_Guide-Encryption-Protecting_Data_at_Rest-File_Based_Encryption">3.3. File Based Encryption</a></span></dt><dt><span class="section"><a href="#Security_Guide-Encryption-Data_in_Motion">3.4. Data in Motion</a></span></dt><dt><span class="section"><a href="#Security_Guide-Encryption-Data_in_Motion-Virtual_Private_Networks">3.5. Virtual Private Networks</a></span></dt><dt><span class="section"><a href="#Security_Guide-Encryption-Data_in_
Motion-Secure_Shell">3.6. Secure Shell</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-LUKS_Disk_Encryption">3.7. LUKS Disk Encryption</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-LUKS_Disk_Encryption-LUKS_Implementation_in_Fedora">3.7.1. LUKS Implementation in Fedora</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-LUKS_Disk_Encryption-Manually_Encrypting_Directories">3.7.2. Manually Encrypting Directories</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-LUKS_Disk_Encryption-Manually_Encrypting_Directories-Step_by_Step_Instructions">3.7.3. Step-by-Step Instructions</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-LUKS_Disk_Encryption-Manually_Encrypting_Directories-What_you_have_just_accomplished">3.7.4. What you have just accomplished.</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-LUKS_Disk_Encryption-Links_of_Interest">3.7.5.
Links of Interest</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-Encryption-7_Zip_Encrypted_Archives">3.8. 7-Zip Encrypted Archives</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Encryption-7_Zip_Encrypted_Archives-Installation">3.8.1. 7-Zip Installation in Fedora</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Encryption-7_Zip_Encrypted_Archives-Installation-Instructions">3.8.2. Step-by-Step Installation Instructions</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Encryption-7_Zip_Encrypted_Archives-Usage_Instructions">3.8.3. Step-by-Step Usage Instructions</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Encryption-7_Zip_Encrypted_Archives-Things_of_note">3.8.4. Things of note</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-Encryption-Using_GPG">3.9. Using GNU Privacy Guard (GnuPG)</a></span></dt><dd><dl><dt>
<span class="section"><a href="#sect-Security_Guide-Encryption-Using_GPG-Keys_in_GNOME">3.9.1. Creating GPG Keys in GNOME</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Encryption-Using_GPG-Creating_GPG_Keys_in_KDE1">3.9.2. Creating GPG Keys in KDE</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Encryption-Using_GPG-Creating_GPG_Keys_in_KDE">3.9.3. Creating GPG Keys Using the Command Line</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Encryption-Using_GPG-About_Public_Key_Encryption">3.9.4. About Public Key Encryption</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#chap-Security_Guide-General_Principles_of_Information_Security">4. General Principles of Information Security</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-General_Principles_of_Information_Security-Tips_Guides_and_Tools">4.1. Tips, Guides, and Tools</a></span></dt></dl></dd><dt><span clas
s="chapter"><a href="#chap-Security_Guide-Secure_Installation">5. Secure Installation</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Secure_Installation-Disk_Partitions">5.1. Disk Partitions</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Secure_Installation-Utilize_LUKS_Partition_Encryption">5.2. Utilize LUKS Partition Encryption</a></span></dt></dl></dd><dt><span class="chapter"><a href="#chap-Security_Guide-Software_Maintenance">6. Software Maintenance</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Software_Maintenance-Install_Minimal_Software">6.1. Install Minimal Software</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Software_Maintenance-Plan_and_Configure_Security_Updates">6.2. Plan and Configure Security Updates</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Software_Maintenance-Plan_and_Configure_Security_Updates-Adjusting_Automatic_
Updates">6.3. Adjusting Automatic Updates</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Software_Maintenance-Install_Signed_Packages_from_Well_Known_Repositories">6.4. Install Signed Packages from Well Known Repositories</a></span></dt></dl></dd><dt><span class="chapter"><a href="#chap-Security_Guide-References">7. References</a></span></dt></dl></div><div xml:lang="en-US" class="preface" title="Preface" lang="en-US"><div class="titlepage"><div><div><h1 id="pref-Security_Guide-Preface" class="title">Preface</h1></div></div></div><div xml:lang="en-US" class="section" title="1. Document Conventions" lang="en-US"><div class="titlepage"><div><div><h2 class="title" id="id639409">1. Document Conventions</h2></div></div></div><div class="para">
This manual uses several conventions to highlight certain words and phrases and draw attention to specific pieces of information.
</div><div class="para">
In PDF and paper editions, this manual uses typefaces drawn from the <a href="https://fedorahosted.org/liberation-fonts/">Liberation Fonts</a> set. The Liberation Fonts set is also used in HTML editions if the set is installed on your system. If not, alternative but equivalent typefaces are displayed. Note: Red Hat Enterprise Linux 5 and later includes the Liberation Fonts set by default.
</div><div class="section" title="1.1. Typographic Conventions"><div class="titlepage"><div><div><h3 class="title" id="id645070">1.1. Typographic Conventions</h3></div></div></div><div class="para">
Four typographic conventions are used to call attention to specific words and phrases. These conventions, and the circumstances they apply to, are as follows.
</div><div class="para">
<code class="literal">Mono-spaced Bold</code>
</div><div class="para">
Used to highlight system input, including shell commands, file names and paths. Also used to highlight keycaps and key combinations. For example:
</div><div class="blockquote"><blockquote class="blockquote"><div class="para">
To see the contents of the file <code class="filename">my_next_bestselling_novel</code> in your current working directory, enter the <code class="command">cat my_next_bestselling_novel</code> command at the shell prompt and press <span class="keycap"><strong>Enter</strong></span> to execute the command.
</div></blockquote></div><div class="para">
The above includes a file name, a shell command and a keycap, all presented in mono-spaced bold and all distinguishable thanks to context.
</div><div class="para">
Key combinations can be distinguished from keycaps by the hyphen connecting each part of a key combination. For example:
</div><div class="blockquote"><blockquote class="blockquote"><div class="para">
Press <span class="keycap"><strong>Enter</strong></span> to execute the command.
</div><div class="para">
Press <span class="keycap"><strong>Ctrl</strong></span>+<span class="keycap"><strong>Alt</strong></span>+<span class="keycap"><strong>F1</strong></span> to switch to the first virtual terminal. Press <span class="keycap"><strong>Ctrl</strong></span>+<span class="keycap"><strong>Alt</strong></span>+<span class="keycap"><strong>F7</strong></span> to return to your X-Windows session.
</div></blockquote></div><div class="para">
The first paragraph highlights the particular keycap to press. The second highlights two key combinations (each a set of three keycaps with each set pressed simultaneously).
</div><div class="para">
If source code is discussed, class names, methods, functions, variable names and returned values mentioned within a paragraph will be presented as above, in <code class="literal">mono-spaced bold</code>. For example:
</div><div class="blockquote"><blockquote class="blockquote"><div class="para">
File-related classes include <code class="classname">filesystem</code> for file systems, <code class="classname">file</code> for files, and <code class="classname">dir</code> for directories. Each class has its own associated set of permissions.
</div></blockquote></div><div class="para">
<span class="application"><strong>Proportional Bold</strong></span>
</div><div class="para">
This denotes words or phrases encountered on a system, including application names; dialog box text; labeled buttons; check-box and radio button labels; menu titles and sub-menu titles. For example:
</div><div class="blockquote"><blockquote class="blockquote"><div class="para">
Choose <span class="guimenu"><strong>System > Preferences > Mouse</strong></span> from the main menu bar to launch <span class="application"><strong>Mouse Preferences</strong></span>. In the <span class="guilabel"><strong>Buttons</strong></span> tab, click the <span class="guilabel"><strong>Left-handed mouse</strong></span> check box and click <span class="guibutton"><strong>Close</strong></span> to switch the primary mouse button from the left to the right (making the mouse suitable for use in the left hand).
</div><div class="para">
To insert a special character into a <span class="application"><strong>gedit</strong></span> file, choose <span class="guimenu"><strong>Applications > Accessories > Character Map</strong></span> from the main menu bar. Next, choose <span class="guimenu"><strong>Search > Find…</strong></span> from the <span class="application"><strong>Character Map</strong></span> menu bar, type the name of the character in the <span class="guilabel"><strong>Search</strong></span> field and click <span class="guibutton"><strong>Next</strong></span>. The character you sought will be highlighted in the <span class="guilabel"><strong>Character Table</strong></span>. Double-click this highlighted character to place it in the <span class="guilabel"><strong>Text to copy</strong></span> field and then click the <span class="guibutton"><strong>Copy</strong></span> button. Now switch back to your document and choose <span class="guimenu"><strong>Edit > Paste</strong></span> from the <
span class="application"><strong>gedit</strong></span> menu bar.
</div></blockquote></div><div class="para">
The above text includes application names; system-wide menu names and items; application-specific menu names; and buttons and text found within a GUI interface, all presented in proportional bold and all distinguishable by context.
</div><div class="para">
Note the <span class="guimenu"><strong>></strong></span> shorthand used to indicate traversal through a menu and its sub-menus. This avoids difficult-to-follow phrasing such as 'Select <span class="guimenuitem"><strong>Mouse</strong></span> from the <span class="guimenu"><strong>Preferences</strong></span> sub-menu in the <span class="guimenu"><strong>System</strong></span> menu of the main menu bar'.
</div><div class="para">
<code class="command"><em class="replaceable"><code>Mono-spaced Bold Italic</code></em></code> or <span class="application"><strong><em class="replaceable"><code>Proportional Bold Italic</code></em></strong></span>
</div><div class="para">
Whether mono-spaced bold or proportional bold, the addition of italics indicates replaceable or variable text. Italics denotes text you do not input literally or displayed text that changes depending on circumstance. For example:
</div><div class="blockquote"><blockquote class="blockquote"><div class="para">
To connect to a remote machine using ssh, type <code class="command">ssh <em class="replaceable"><code>username</code></em>@<em class="replaceable"><code>domain.name</code></em></code> at a shell prompt. If the remote machine is <code class="filename">example.com</code> and your username on that machine is john, type <code class="command">ssh john at example.com</code>.
</div><div class="para">
The <code class="command">mount -o remount <em class="replaceable"><code>file-system</code></em></code> command remounts the named file system. For example, to remount the <code class="filename">/home</code> file system, the command is <code class="command">mount -o remount /home</code>.
</div><div class="para">
To see the version of a currently installed package, use the <code class="command">rpm -q <em class="replaceable"><code>package</code></em></code> command. It will return a result as follows: <code class="command"><em class="replaceable"><code>package-version-release</code></em></code>.
</div></blockquote></div><div class="para">
Note the words in bold italics above — username, domain.name, file-system, package, version and release. Each word is a placeholder, either for text you enter when issuing a command or for text displayed by the system.
</div><div class="para">
Aside from standard usage for presenting the title of a work, italics denotes the first use of a new and important term. For example:
</div><div class="blockquote"><blockquote class="blockquote"><div class="para">
When the Apache HTTP Server accepts requests, it dispatches child processes or threads to handle them. This group of child processes or threads is known as a <em class="firstterm">server-pool</em>. Under Apache HTTP Server 2.0, the responsibility for creating and maintaining these server-pools has been abstracted to a group of modules called <em class="firstterm">Multi-Processing Modules</em> (<em class="firstterm">MPMs</em>). Unlike other modules, only one module from the MPM group can be loaded by the Apache HTTP Server.
</div></blockquote></div></div><div class="section" title="1.2. Pull-quote Conventions"><div class="titlepage"><div><div><h3 class="title" id="id591154">1.2. Pull-quote Conventions</h3></div></div></div><div class="para">
Terminal output and source code listings are set off visually from the surrounding text.
</div><div class="para">
Output sent to a terminal is set in <code class="computeroutput">mono-spaced roman</code> and presented thus:
</div><pre class="screen">books Desktop documentation drafts mss photos stuff svn
books_tests Desktop1 downloads images notes scripts svgs
</pre><div class="para">
Source-code listings are also set in <code class="computeroutput">mono-spaced roman</code> but add syntax highlighting as follows:
</div><pre class="programlisting"><pre class="programlisting">package org.<span class="perl_Function">jboss</span>.<span class="perl_Function">book</span>.<span class="perl_Function">jca</span>.<span class="perl_Function">ex1</span>;
<span class="perl_Keyword">import</span> javax.naming.InitialContext;
<span class="perl_Keyword">public</span> <span class="perl_Keyword">class</span> ExClient
{
<span class="perl_Keyword">public</span> <span class="perl_DataType">static</span> <span class="perl_DataType">void</span> <span class="perl_Function">main</span>(String args[])
<span class="perl_Keyword">throws</span> Exception
{
InitialContext iniCtx = <span class="perl_Keyword">new</span> InitialContext();
Object ref = iniCtx.<span class="perl_Function">lookup</span>(<span class="perl_String">"EchoBean"</span>);
EchoHome home = (EchoHome) ref;
Echo echo = home.<span class="perl_Function">create</span>();
System.<span class="perl_Function">out</span>.<span class="perl_Function">println</span>(<span class="perl_String">"Created Echo"</span>);
System.<span class="perl_Function">out</span>.<span class="perl_Function">println</span>(<span class="perl_String">"Echo.echo('Hello') = "</span> + echo.<span class="perl_Function">echo</span>(<span class="perl_String">"Hello"</span>));
}
}
</pre></pre></div><div class="section" title="1.3. Notes and Warnings"><div class="titlepage"><div><div><h3 class="title" id="id645085">1.3. Notes and Warnings</h3></div></div></div><div class="para">
Finally, we use three visual styles to draw attention to information that might otherwise be overlooked.
</div><div class="note"><h2>Note</h2><div class="para">
Notes are tips, shortcuts or alternative approaches to the task at hand. Ignoring a note should have no negative consequences, but you might miss out on a trick that makes your life easier.
</div></div><div class="important"><h2>Important</h2><div class="para">
Important boxes detail things that are easily missed: configuration changes that only apply to the current session, or services that need restarting before an update will apply. Ignoring a box labeled 'Important' won't cause data loss but may cause irritation and frustration.
</div></div><div class="warning"><h2>Warning</h2><div class="para">
Warnings should not be ignored. Ignoring warnings will most likely cause data loss.
</div></div></div></div><div xml:lang="en-US" class="section" title="2. We Need Feedback!" lang="en-US"><div class="titlepage"><div><div><h2 class="title" id="We_Need_Feedback">2. We Need Feedback!</h2></div></div></div><div class="para">
More information about the Linux Security Guide project can be found at <a href="https://fedorahosted.org/securityguide">https://fedorahosted.org/securityguide</a>
</div><div class="para">
To provide feedback for the Security Guide, please file a bug in <a href="https://bugzilla.redhat.com/enter_bug.cgi?component=security-guide&product=Fedora%20Documentation">https://bugzilla.redhat.com/enter_bug.cgi?component=security-guide&product=Fedora%20Documentation</a>. Please select the proper component in the dropdown menu which should be the page name.
</div></div></div><div xml:lang="en-US" class="chapter" title="Chapter 1. Security Overview" lang="en-US"><div class="titlepage"><div><div><h2 class="title" id="chap-Security_Guide-Security_Overview">Chapter 1. Security Overview</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#sect-Security_Guide-Introduction_to_Security">1.1. Introduction to Security</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Introduction_to_Security-What_is_Computer_Security">1.1.1. What is Computer Security?</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Introduction_to_Security-SELinux">1.1.2. SELinux</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Introduction_to_Security-Security_Controls">1.1.3. Security Controls</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Introduction_to_Security-Conclusion">1.1.4. Conclusion</a></span></dt></dl></dd><dt><span class="section"
><a href="#sect-Security_Guide-Vulnerability_Assessment">1.2. Vulnerability Assessment</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Vulnerability_Assessment-Thinking_Like_the_Enemy">1.2.1. Thinking Like the Enemy</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Vulnerability_Assessment-Defining_Assessment_and_Testing">1.2.2. Defining Assessment and Testing</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Vulnerability_Assessment-Evaluating_the_Tools">1.2.3. Evaluating the Tools</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-Attackers_and_Vulnerabilities">1.3. Attackers and Vulnerabilities</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Attackers_and_Vulnerabilities-A_Quick_History_of_Hackers">1.3.1. A Quick History of Hackers</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Attackers_and_Vulnerabilities-Threats_t
o_Network_Security">1.3.2. Threats to Network Security</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Attackers_and_Vulnerabilities-Threats_to_Server_Security">1.3.3. Threats to Server Security</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Attackers_and_Vulnerabilities-Threats_to_Workstation_and_Home_PC_Security">1.3.4. Threats to Workstation and Home PC Security</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-Security_Guide-Common_Exploits_and_Attacks">1.4. Common Exploits and Attacks</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Security_Updates">1.5. Security Updates</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-Security_Guide-Security_Updates-Updating_Packages">1.5.1. Updating Packages</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Updating_Packages-Verifying_Signed_Packages">1.5.2. Verifying Signed Packages</a></span></dt><dt><span class=
"section"><a href="#sect-Security_Guide-Updating_Packages-Installing_Signed_Packages">1.5.3. Installing Signed Packages</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Updating_Packages-Applying_the_Changes">1.5.4. Applying the Changes</a></span></dt></dl></dd></dl></div><div class="para">
Because of the increased reliance on powerful, networked computers to help run businesses and keep track of our personal information, entire industries have been formed around the practice of network and computer security. Enterprises have solicited the knowledge and skills of security experts to properly audit systems and tailor solutions to fit the operating requirements of the organization. Because most organizations are increasingly dynamic in nature, with workers accessing company IT resources locally and remotely, the need for secure computing environments has become more pronounced.
</div><div class="para">
Unfortunately, most organizations (as well as individual users) regard security as an afterthought, a process that is overlooked in favor of increased power, productivity, and budgetary concerns. Proper security implementation is often enacted postmortem — <span class="emphasis"><em>after</em></span> an unauthorized intrusion has already occurred. Security experts agree that taking the correct measures prior to connecting a site to an untrusted network, such as the Internet, is an effective means of thwarting most attempts at intrusion.
</div><div xml:lang="en-US" class="section" title="1.1. Introduction to Security" lang="en-US"><div class="titlepage"><div><div><h2 class="title" id="sect-Security_Guide-Introduction_to_Security">1.1. Introduction to Security</h2></div></div></div><div class="section" title="1.1.1. What is Computer Security?"><div class="titlepage"><div><div><h3 class="title" id="sect-Security_Guide-Introduction_to_Security-What_is_Computer_Security">1.1.1. What is Computer Security?</h3></div></div></div><div class="para">
Computer security is a general term that covers a wide area of computing and information processing. Industries that depend on computer systems and networks to conduct daily business transactions and access crucial information regard their data as an important part of their overall assets. Several terms and metrics have entered our daily business vocabulary, such as total cost of ownership (TCO) and quality of service (QoS). Using these metrics, industries can calculate aspects such as data integrity and high-availability as part of their planning and process management costs. In some industries, such as electronic commerce, the availability and trustworthiness of data can be the difference between success and failure.
</div><div class="section" title="1.1.1.1. How did Computer Security Come about?"><div class="titlepage"><div><div><h4 class="title" id="sect-Security_Guide-What_is_Computer_Security-How_did_Computer_Security_Come_about">1.1.1.1. How did Computer Security Come about?</h4></div></div></div><div class="para">
Information security has evolved over the years due to the increasing reliance on public networks not to disclose personal, financial, and other restricted information. There are numerous instances such as the Mitnick <sup>[<a id="id643094" href="#ftn.id643094" class="footnote">1</a>]</sup>and the Vladimir Levin <sup>[<a id="id643086" href="#ftn.id643086" class="footnote">2</a>]</sup>cases that prompted organizations across all industries to re-think the way they handle information, as well as its transmission and disclosure. The popularity of the Internet was one of the most important developments that prompted an intensified effort in data security.
</div><div class="para">
An ever-growing number of people are using their personal computers to gain access to the resources that the Internet has to offer. From research and information retrieval to electronic mail and commerce transaction, the Internet has been regarded as one of the most important developments of the 20th century.
</div><div class="para">
The Internet and its earlier protocols, however, were developed as a <em class="firstterm">trust-based</em> system. That is, the Internet Protocol was not designed to be secure in itself. There are no approved security standards built into the TCP/IP communications stack, leaving it open to potentially malicious users and processes across the network. Modern developments have made Internet communication more secure, but there are still several incidents that gain national attention and alert us to the fact that nothing is completely safe.
</div></div><div class="section" title="1.1.1.2. Security Today"><div class="titlepage"><div><div><h4 class="title" id="sect-Security_Guide-What_is_Computer_Security-Security_Today">1.1.1.2. Security Today</h4></div></div></div><div class="para">
In February of 2000, a Distributed Denial of Service (DDoS) attack was unleashed on several of the most heavily-trafficked sites on the Internet. The attack rendered yahoo.com, cnn.com, amazon.com, fbi.gov, and several other sites completely unreachable to normal users, as it tied up routers for several hours with large-byte ICMP packet transfers, also called a <em class="firstterm">ping flood</em>. The attack was brought on by unknown assailants using specially created, widely available programs that scanned vulnerable network servers, installed client applications called <em class="firstterm">trojans</em> on the servers, and timed an attack with every infected server flooding the victim sites and rendering them unavailable. Many blame the attack on fundamental flaws in the way routers and the protocols used are structured to accept all incoming data, no matter where or for what purpose the packets are sent.
</div><div class="para">
In 2007, a data breach exploiting the widely-known weaknesses of the Wired Equivalent Privacy (WEP) wireless encryption protocol resulted in the theft from a global financial institution of over 45 million credit card numbers.<sup>[<a id="id1043869" href="#ftn.id1043869" class="footnote">3</a>]</sup>
</div><div class="para">
In a separate incident, the billing records of over 2.2 million patients stored on a backup tape were stolen from the front seat of a courier's car.<sup>[<a id="id1043866" href="#ftn.id1043866" class="footnote">4</a>]</sup>
</div><div class="para">
Currently, an estimated 1.4 billion people use or have used the Internet worldwide.<sup>[<a id="id1043807" href="#ftn.id1043807" class="footnote">5</a>]</sup> At the same time:
</div><div class="itemizedlist"><ul><li class="listitem"><div class="para">
On any given day, there are approximately 225 major incidences of security breach reported to the CERT Coordination Center at Carnegie Mellon University.<sup>[<a id="id1043837" href="#ftn.id1043837" class="footnote">6</a>]</sup>
</div></li><li class="listitem"><div class="para">
In 2003, the number of CERT reported incidences jumped to 137,529 from 82,094 in 2002 and from 52,658 in 2001.<sup>[<a id="id1043825" href="#ftn.id1043825" class="footnote">7</a>]</sup>
</div></li><li class="listitem"><div class="para">
The worldwide economic impact of the three most dangerous Internet Viruses of the last three years was estimated at US$13.2 Billion.<sup>[<a id="id1043810" href="#ftn.id1043810" class="footnote">8</a>]</sup>
</div></li></ul></div><div class="para">
From a 2008 global survey of business and technology executives "The Global State of Information Security"<sup>[<a id="id1043796" href="#ftn.id1043796" class="footnote">9</a>]</sup>, undertaken by <span class="emphasis"><em>CIO Magazine</em></span>, some points are:
</div><div class="itemizedlist"><ul><li class="listitem"><div class="para">
Just 43% of respondents audit or monitor user compliance with security policies
</div></li><li class="listitem"><div class="para">
Only 22% keep an inventory of the outside companies that use their data
</div></li><li class="listitem"><div class="para">
The source of nearly half of security incidents was marked as "Unknown"
</div></li><li class="listitem"><div class="para">
44% of respondents plan to increase security spending in the next year
</div></li><li class="listitem"><div class="para">
59% have an information security strategy
</div></li></ul></div><div class="para">
These results enforce the reality that computer security has become a quantifiable and justifiable expense for IT budgets. Organizations that require data integrity and high availability elicit the skills of system administrators, developers, and engineers to ensure 24x7 reliability of their systems, services, and information. Falling victim to malicious users, processes, or coordinated attacks is a direct threat to the success of the organization.
</div><div class="para">
Unfortunately, system and network security can be a difficult proposition, requiring an intricate knowledge of how an organization regards, uses, manipulates, and transmits its information. Understanding the way an organization (and the people that make up the organization) conducts business is paramount to implementing a proper security plan.
</div></div><div class="section" title="1.1.1.3. Standardizing Security"><div class="titlepage"><div><div><h4 class="title" id="sect-Security_Guide-What_is_Computer_Security-Standardizing_Security">1.1.1.3. Standardizing Security</h4></div></div></div><div class="para">
Enterprises in every industry rely on regulations and rules that are set by standards-making bodies such as the American Medical Association (AMA) or the Institute of Electrical and Electronics Engineers (IEEE). The same ideals hold true for information security. Many security consultants and vendors agree upon the standard security model known as CIA, or <em class="firstterm">Confidentiality, Integrity, and Availability</em>. This three-tiered model is a generally accepted component to assessing risks of sensitive information and establishing security policy. The following describes the CIA model in further detail:
</div><div class="itemizedlist"><ul><li class="listitem"><div class="para">
Confidentiality — Sensitive information must be available only to a set of pre-defined individuals. Unauthorized transmission and usage of information should be restricted. For example, confidentiality of information ensures that a customer's personal or financial information is not obtained by an unauthorized individual for malicious purposes such as identity theft or credit fraud.
</div></li><li class="listitem"><div class="para">
Integrity — Information should not be altered in ways that render it incomplete or incorrect. Unauthorized users should be restricted from the ability to modify or destroy sensitive information.
</div></li><li class="listitem"><div class="para">
Availability — Information should be accessible to authorized users any time that it is needed. Availability is a warranty that information can be obtained with an agreed-upon frequency and timeliness. This is often measured in terms of percentages and agreed to formally in Service Level Agreements (SLAs) used by network service providers and their enterprise clients.
</div></li></ul></div></div></div><div class="section" title="1.1.2. SELinux"><div class="titlepage"><div><div><h3 class="title" id="sect-Security_Guide-Introduction_to_Security-SELinux">1.1.2. SELinux</h3></div></div></div><div class="para">
Fedora includes an enhancement to the Linux kernel called SELinux, which implements a Mandatory Access Control (MAC) architecture that provides a fine-grained level of control over files, processes, users and applications in the system. Detailed discussion of SELinux is beyond the scope of this document; however, for more information on SELinux and its use in Fedora, refer to the Fedora SELinux User Guide available at <a href="http://docs.fedoraproject.org/selinux-user-guide/">http://docs.fedoraproject.org/selinux-user-guide/</a>. For more information on configuring and running services in Fedora that are protected by SELinux, refer to the SELinux Managing Confined Services Guide available at <a href="http://docs.fedoraproject.org/selinux-managing-confined-services-guide/">http://docs.fedoraproject.org/selinux-managing-confined-services-guide</a>. Other available resources for SELinux are listed in <a class="xref" href="#chap-Security_Guide-References" title="Chapter 7.Â
References">Chapter 7, <i>References</i></a>.
</div></div><div class="section" title="1.1.3. Security Controls"><div class="titlepage"><div><div><h3 class="title" id="sect-Security_Guide-Introduction_to_Security-Security_Controls">1.1.3. Security Controls</h3></div></div></div><div class="para">
Computer security is often divided into three distinct master categories, commonly referred to as <em class="wordasword">controls</em>:
</div><div class="itemizedlist"><ul><li class="listitem"><div class="para">
Physical
</div></li><li class="listitem"><div class="para">
Technical
</div></li><li class="listitem"><div class="para">
Administrative
</div></li></ul></div><div class="para">
These three broad categories define the main objectives of proper security implementation. Within these controls are sub-categories that further detail the controls and how to implement them.
</div><div class="section" title="1.1.3.1. Physical Controls"><div class="titlepage"><div><div><h4 class="title" id="sect-Security_Guide-Security_Controls-Physical_Controls">1.1.3.1. Physical Controls</h4></div></div></div><div class="para">
Physical control is the implementation of security measures in a defined structure used to deter or prevent unauthorized access to sensitive material. Examples of physical controls are:
</div><div class="itemizedlist"><ul><li class="listitem"><div class="para">
Closed-circuit surveillance cameras
</div></li><li class="listitem"><div class="para">
Motion or thermal alarm systems
</div></li><li class="listitem"><div class="para">
Security guards
</div></li><li class="listitem"><div class="para">
Picture IDs
</div></li><li class="listitem"><div class="para">
Locked and dead-bolted steel doors
[...3810 lines suppressed...]
<a href="http://clemens.endorphin.org/LUKS/">LUKS - Linux Unified Key Setup</a>
</div></li><li class="listitem"><div class="para">
<a href="https://bugzilla.redhat.com/attachment.cgi?id=161912">HOWTO: Creating an encrypted Physical Volume (PV) using a second hard drive, pvmove, and a Fedora LiveCD</a>
</div></li></ul></div></div></div><div xml:lang="en-US" class="section" title="3.8. 7-Zip Encrypted Archives" lang="en-US"><div class="titlepage"><div><div><h2 class="title" id="sect-Security_Guide-Encryption-7_Zip_Encrypted_Archives">3.8. 7-Zip Encrypted Archives</h2></div></div></div><div class="para">
<a href="http://www.7-zip.org/">7-Zip</a> is a cross-platform, next generation, file compression tool that can also use strong encryption (AES-256) to protect the contents of the archive. This is extremely useful when you need to move data between multiple computers that use varying operating systems (i.e. Linux at home, Windows at work) and you want a portable encryption solution.
</div><div class="section" title="3.8.1. 7-Zip Installation in Fedora"><div class="titlepage"><div><div><h3 class="title" id="sect-Security_Guide-Encryption-7_Zip_Encrypted_Archives-Installation">3.8.1. 7-Zip Installation in Fedora</h3></div></div></div><div class="para">
7-Zip is not a base package in Fedora, but it is available in the software repository. Once installed, the package will update alongside the rest of the software on the computer with no special attention necessary.
</div></div><div class="section" title="3.8.2. Step-by-Step Installation Instructions"><div class="titlepage"><div><div><h3 class="title" id="sect-Security_Guide-Encryption-7_Zip_Encrypted_Archives-Installation-Instructions">3.8.2. Step-by-Step Installation Instructions</h3></div></div></div><div class="itemizedlist"><ul><li class="listitem"><div class="para">
Open a Terminal: <code class="code">Click ''Applications'' -> ''System Tools'' -> ''Terminal''</code>
</div></li><li class="listitem"><div class="para">
Install 7-Zip with sudo access: <code class="code">sudo yum install p7zip</code>
</div></li><li class="listitem"><div class="para">
Close the Terminal: <code class="code">exit</code>
</div></li></ul></div></div><div class="section" title="3.8.3. Step-by-Step Usage Instructions"><div class="titlepage"><div><div><h3 class="title" id="sect-Security_Guide-Encryption-7_Zip_Encrypted_Archives-Usage_Instructions">3.8.3. Step-by-Step Usage Instructions</h3></div></div></div><div class="para">
By following these instructions you are going to compress and encrypt your "Documents" directory. Your original "Documents" directory will remain unaltered. This technique can be applied to any directory or file you have access to on the filesystem.
</div><div class="itemizedlist"><ul><li class="listitem"><div class="para">
Open a Terminal:<code class="code">Click ''Applications'' -> ''System Tools'' -> ''Terminal''</code>
</div></li><li class="listitem"><div class="para">
Compress and Encrypt: (enter a password when prompted) <code class="code">7za a -mhe=on -ms=on -p Documents.7z Documents/</code>
</div></li></ul></div><div class="para">
The "Documents" directory is now compressed and encrypted. The following instructions will move the encrypted archive somewhere new and then extract it.
</div><div class="itemizedlist"><ul><li class="listitem"><div class="para">
Create a new directory: <code class="code">mkdir newplace</code>
</div></li><li class="listitem"><div class="para">
Move the encrypted file: <code class="code">mv Documents.7z newplace</code>
</div></li><li class="listitem"><div class="para">
Go to the new directory: <code class="code">cd newplace</code>
</div></li><li class="listitem"><div class="para">
Extract the file: (enter the password when prompted) <code class="code">7za x Documents.7z</code>
</div></li></ul></div><div class="para">
The archive is now extracted into the new location. The following instructions will clean up all the prior steps and restore your computer to its previous state.
</div><div class="itemizedlist"><ul><li class="listitem"><div class="para">
Go up a directory: <code class="code">cd ..</code>
</div></li><li class="listitem"><div class="para">
Delete the test archive and test extraction: <code class="code">rm -r newplace</code>
</div></li><li class="listitem"><div class="para">
Close the Terminal: <code class="code">exit</code>
</div></li></ul></div></div><div class="section" title="3.8.4. Things of note"><div class="titlepage"><div><div><h3 class="title" id="sect-Security_Guide-Encryption-7_Zip_Encrypted_Archives-Things_of_note">3.8.4. Things of note</h3></div></div></div><div class="para">
7-Zip is not shipped by default with Microsoft Windows or Mac OS X. If you need to use your 7-Zip files on those platforms you will need to install the appropriate version of 7-Zip on those computers. See the 7-Zip <a href="http://www.7-zip.org/download.html">download page</a>.
</div><div class="para">
GNOME's File Roller application will recognize your .7z files and attempt to open them, but it will fail with the error "''An error occurred while loading the archive.''" when it attempts to do so. This is because File Roller does not currently support the extraction of encrypted 7-Zip files. A bug report ([http://bugzilla.gnome.org/show_bug.cgi?id=490732 Gnome Bug 490732]) has been submitted.
</div></div></div><div xml:lang="en-US" class="section" title="3.9. Using GNU Privacy Guard (GnuPG)" lang="en-US"><div class="titlepage"><div><div><h2 class="title" id="sect-Security_Guide-Encryption-Using_GPG">3.9. Using GNU Privacy Guard (GnuPG)</h2></div></div></div><div class="para">
GPG is used to identify yourself and authenticate your communications, including those with people you don't know. GPG allows anyone reading a GPG-signed email to verify its authenticity. In other words, GPG allows someone to be reasonably certain that communications signed by you actually are from you. GPG is useful because it helps prevent third parties from altering code or intercepting conversations and altering the message.
</div><div class="section" title="3.9.1. Creating GPG Keys in GNOME"><div class="titlepage"><div><div><h3 class="title" id="sect-Security_Guide-Encryption-Using_GPG-Keys_in_GNOME">3.9.1. Creating GPG Keys in GNOME</h3></div></div></div><div class="para">
Install the Seahorse utility, which makes GPG key management easier. From the main menu, select <code class="code">System > Administration > Add/Remove Software</code> and wait for PackageKit to start. Enter <code class="code">Seahorse</code> into the text box and select the Find. Select the checkbox next to the ''seahorse'' package and select ''Apply'' to add the software. You can also install <code class="code">Seahorse</code> at the command line with the command <code class="code">su -c "yum install seahorse"</code>.
</div><div class="para">
To create a key, from the ''Applications > Accessories'' menu select ''Passwords and Encryption Keys'', which starts the application <code class="code">Seahorse</code>. From the ''Key'' menu select ''Create New Key...'' then ''PGP Key'' then click ''Continue''. Type your full name, email address, and an optional comment describing who are you (e.g.: John C. Smith, jsmith at example.com, The Man). Click ''Create''. A dialog is displayed asking for a passphrase for the key. Choose a strong passphrase but also easy to remember. Click ''OK'' and the key is created.
</div><div class="warning"><h2>Warning</h2><div class="para">
If you forget your passphrase, the key cannot be used and any data encrypted using that key will be lost.
</div></div><div class="para">
To find your GPG key ID, look in the ''Key ID'' column next to the newly created key. In most cases, if you are asked for the key ID, you should prepend "0x" to the key ID, as in "0x6789ABCD". You should make a backup of your private key and store it somewhere secure.
</div></div><div class="section" title="3.9.2. Creating GPG Keys in KDE"><div class="titlepage"><div><div><h3 class="title" id="sect-Security_Guide-Encryption-Using_GPG-Creating_GPG_Keys_in_KDE1">3.9.2. Creating GPG Keys in KDE</h3></div></div></div><div class="para">
Start the KGpg program from the main menu by selecting Applications > Utilities > Encryption Tool. If you have never used KGpg before, the program walks you through the process of creating your own GPG keypair. A dialog box appears prompting you to create a new key pair. Enter your name, email address, and an optional comment. You can also choose an expiration time for your key, as well as the key strength (number of bits) and algorithms. The next dialog box prompts you for your passphrase. At this point, your key appears in the main <code class="code">KGpg</code> window.
</div><div class="warning"><h2>Warning</h2><div class="para">
If you forget your passphrase, the key cannot be used and any data encrypted using that key will be lost.
</div></div><div class="para">
To find your GPG key ID, look in the ''Key ID'' column next to the newly created key. In most cases, if you are asked for the key ID, you should prepend "0x" to the key ID, as in "0x6789ABCD". You should make a backup of your private key and store it somewhere secure.
</div></div><div class="section" title="3.9.3. Creating GPG Keys Using the Command Line"><div class="titlepage"><div><div><h3 class="title" id="sect-Security_Guide-Encryption-Using_GPG-Creating_GPG_Keys_in_KDE">3.9.3. Creating GPG Keys Using the Command Line</h3></div></div></div><div class="para">
Use the following shell command: <code class="code">gpg --gen-key</code>
</div><div class="para">
This command generates a key pair that consists of a public and a private key. Other people use your public key to authenticate and/or decrypt your communications. Distribute your public key as widely as possible, especially to people who you know will want to receive authentic communications from you, such as a mailing list. The Fedora Documentation Project, for example, asks participants to include a GPG public key in their self-introduction.
</div><div class="para">
A series of prompts directs you through the process. Press the <code class="code">Enter</code> key to assign a default value if desired. The first prompt asks you to select what kind of key you prefer:
</div><div class="para">
Please select what kind of key you want: (1) DSA and ElGamal (default) (2) DSA (sign only) (4) RSA (sign only) Your selection? In almost all cases, the default is the correct choice. A DSA/ElGamal key allows you not only to sign communications, but also to encrypt files.
</div><div class="para">
Next, choose the key size: minimum keysize is 768 bits default keysize is 1024 bits highest suggested keysize is 2048 bits What keysize do you want? (1024) Again, the default is sufficient for almost all users, and represents an ''extremely'' strong level of security.
</div><div class="para">
Next, choose when the key will expire. It is a good idea to choose an expiration date instead of using the default, which is ''none.'' If, for example, the email address on the key becomes invalid, an expiration date will remind others to stop using that public key.
</div><div class="para">
Please specify how long the key should be valid. 0 = key does not expire d = key expires in n days w = key expires in n weeks m = key expires in n months y = key expires in n years Key is valid for? (0)
</div><div class="para">
Entering a value of <code class="code">1y</code>, for example, makes the key valid for one year. (You may change this expiration date after the key is generated, if you change your mind.)
</div><div class="para">
Before the <code class="code">gpg</code>code> program asks for signature information, the following prompt appears: <code class="code">Is this correct (y/n)?</code> Enter <code class="code">y</code>code> to finish the process.
</div><div class="para">
Next, enter your name and email address. Remember this process is about authenticating you as a real individual. For this reason, include your real name. Do not use aliases or handles, since these disguise or obfuscate your identity.
</div><div class="para">
Enter your real email address for your GPG key. If you choose a bogus email address, it will be more difficult for others to find your public key. This makes authenticating your communications difficult. If you are using this GPG key for [[DocsProject/SelfIntroduction| self-introduction]] on a mailing list, for example, enter the email address you use on that list.
</div><div class="para">
Use the comment field to include aliases or other information. (Some people use different keys for different purposes and identify each key with a comment, such as "Office" or "Open Source Projects.")
</div><div class="para">
At the confirmation prompt, enter the letter O to continue if all entries are correct, or use the other options to fix any problems. Finally, enter a passphrase for your secret key. The <code class="code">gpg</code> program asks you to enter your passphrase twice to ensure you made no typing errors.
</div><div class="para">
Finally, <code class="code">gpg</code> generates random data to make your key as unique as possible. Move your mouse, type random keys, or perform other tasks on the system during this step to speed up the process. Once this step is finished, your keys are complete and ready to use:
</div><pre class="screen">
pub 1024D/1B2AFA1C 2005-03-31 John Q. Doe (Fedora Docs Project) <jqdoe at example.com>
Key fingerprint = 117C FE83 22EA B843 3E86 6486 4320 545E 1B2A FA1C
sub 1024g/CEA4B22E 2005-03-31 [expires: 2006-03-31]
</pre><div class="para">
The key fingerprint is a shorthand "signature" for your key. It allows you to confirm to others that they have received your actual public key without any tampering. You do not need to write this fingerprint down. To display the fingerprint at any time, use this command, substituting your email address: <code class="code"> gpg --fingerprint jqdoe at example.com </code>
</div><div class="para">
Your "GPG key ID" consists of 8 hex digits identifying the public key. In the example above, the GPG key ID is 1B2AFA1C. In most cases, if you are asked for the key ID, you should prepend "0x" to the key ID, as in "0x1B2AFA1C".
</div><div class="warning"><h2>Warning</h2><div class="para">
If you forget your passphrase, the key cannot be used and any data encrypted using that key will be lost.
</div></div></div><div class="section" title="3.9.4. About Public Key Encryption"><div class="titlepage"><div><div><h3 class="title" id="sect-Security_Guide-Encryption-Using_GPG-About_Public_Key_Encryption">3.9.4. About Public Key Encryption</h3></div></div></div><div class="orderedlist"><ol><li class="listitem"><div class="para">
<a href="http://en.wikipedia.org/wiki/Public-key_cryptography">Wikipedia - Public Key Cryptography</a>
</div></li><li class="listitem"><div class="para">
<a href="http://computer.howstuffworks.com/encryption.htm">HowStuffWorks - Encryption</a>
</div></li></ol></div></div></div></div><div xml:lang="en-US" class="chapter" title="Chapter 4. General Principles of Information Security" lang="en-US"><div class="titlepage"><div><div><h2 class="title" id="chap-Security_Guide-General_Principles_of_Information_Security">Chapter 4. General Principles of Information Security</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#sect-Security_Guide-General_Principles_of_Information_Security-Tips_Guides_and_Tools">4.1. Tips, Guides, and Tools</a></span></dt></dl></div><div class="para">
The following general principals provide an overview of good security practices:
</div><div class="itemizedlist"><ul><li class="listitem"><div class="para">
encrypt all data transmitted over networks to help prevent man-in-the-middle attacks and eavesdropping. It is important to encrypt authentication information, such as passwords.
</div></li><li class="listitem"><div class="para">
minimize the amount of software installed and running services.
</div></li><li class="listitem"><div class="para">
use security-enhancing software and tools, for example, Security-Enhanced Linux (SELinux) for Mandatory Access Control (MAC), Netfilter iptables for packet filtering (firewall), and the GNU Privacy Guard (GnuPG) for encrypting files.
</div></li><li class="listitem"><div class="para">
if possible, run each network service on a separate system to minimize the risk of one compromised service being used to compromise other services.
</div></li><li class="listitem"><div class="para">
maintain user accounts: create and enforce a strong password policy; delete unused user accounts.
</div></li><li class="listitem"><div class="para">
routinely review system and application logs. By default, security-relevant system logs are written to <code class="filename">/var/log/secure</code> and <code class="filename">/var/log/audit/audit.log</code>. Note: sending logs to a dedicated log server helps prevent attackers from easily modifying local logs to avoid detection.
</div></li><li class="listitem"><div class="para">
never log in as the root user unless absolutely necessary. It is recommended that administrators use <code class="command">sudo</code> to execute commands as root when required. Users capable of running <code class="command">sudo</code> are specified in <code class="filename">/etc/sudoers</code>. Use the <code class="command">visudo</code> utility to edit <code class="filename">/etc/sudoers</code>.
</div></li></ul></div><div class="section" title="4.1. Tips, Guides, and Tools"><div class="titlepage"><div><div><h2 class="title" id="sect-Security_Guide-General_Principles_of_Information_Security-Tips_Guides_and_Tools">4.1. Tips, Guides, and Tools</h2></div></div></div><div class="para">
The United States' <a href="http://www.nsa.gov/">National Security Agency (NSA)</a> provides hardening guides and tips for many different operating systems, to help government agencies, businesses, and individuals secure their systems against attack. The following guides (in PDF format) provide guidance for Red Hat Enterprise Linux 5:
</div><div class="itemizedlist"><ul><li class="listitem"><div class="para">
<a href="http://www.nsa.gov/ia/_files/os/redhat/rhel5-pamphlet-i731.pdf">Hardening Tips for the Red Hat Enterprise Linux 5</a>
</div></li><li class="listitem"><div class="para">
<a href="http://www.nsa.gov/ia/_files/os/redhat/rhel5-guide-i731.pdf">Guide to the Secure Configuration of Red Hat Enterprise Linux 5</a>
</div></li></ul></div><div class="para">
The <a href="http://www.disa.mil/">Defense Information Systems Agency (DISA)</a> provides documentation, checklists, and tests to help secure your system (<a href="http://iase.disa.mil/index2.html">Information Assurance Support Environment</a>). The <a href="http://iase.disa.mil/stigs/stig/unix-stig-v5r1.pdf">UNIX SECURITY TECHNICAL IMPLEMENTATION GUIDE</a> (PDF) is a very specific guide to UNIX security - an advanced knowledge of UNIX and Linux is recommended before reading this guide.
</div><div class="para">
The DISA <a href="http://iase.disa.mil/stigs/checklist/unix_checklist_v5r1-16_20090215.ZIP">UNIX Security Checklist Version 5, Release 1.16</a> provides a collection of documents and checklists, ranging from the correct ownerships and modes for system files, to patch control.
</div><div class="para">
Also, DISA has made available <a href="http://iase.disa.mil/stigs/SRR/unix.html">UNIX SPR scripts</a> that allow administrators to check specific settings on systems. These scripts provide XML-formatted reports listing any known vulnerable settings.
</div></div></div><div xml:lang="en-US" class="chapter" title="Chapter 5. Secure Installation" lang="en-US"><div class="titlepage"><div><div><h2 class="title" id="chap-Security_Guide-Secure_Installation">Chapter 5. Secure Installation</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#sect-Security_Guide-Secure_Installation-Disk_Partitions">5.1. Disk Partitions</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Secure_Installation-Utilize_LUKS_Partition_Encryption">5.2. Utilize LUKS Partition Encryption</a></span></dt></dl></div><div class="para">
Security begins with the first time you put that CD or DVD into your disk drive to install Fedora. Configuring your system securely from the beginning makes it easier to implement additional security settings later.
</div><div class="section" title="5.1. Disk Partitions"><div class="titlepage"><div><div><h2 class="title" id="sect-Security_Guide-Secure_Installation-Disk_Partitions">5.1. Disk Partitions</h2></div></div></div><div class="para">
The NSA recommends creating separate partitions for /boot, /, /home, /tmp, and /var/tmp. The reasons for each are different and we will address each partition.
</div><div class="para">
/boot - This partition is the first partition that is read by the system during boot up. The boot loader and kernel images that are used to boot your system into Fedora are stored in this partition. This partition should not be encrypted. If this partition is included in / and that partition is encrypted or otherwise becomes unavailable then your system will not be able to boot.
</div><div class="para">
/home - When user data (/home) is stored in / instead of in a separate partition, the partition can fill up causing the operating system to become unstable. Also, when upgrading your system to the next version of Fedora it is a lot easier when you can keep your data in the /home partition as it will not be overwritten during installation. If the root partition (/) becomes corrupt your data could be lost forever. By using a separate partition there is slightly more protection against data loss. You can also target this partition for frequent backups.
</div><div class="para">
/tmp and /var/tmp - Both the /tmp and the /var/tmp directories are used to store data that doesn't need to be stored for a long period of time. However if a lot of data floods one of these directories it can consume all of your storage space. If this happens and these directories are stored within / then your system could become unstable and crash. For this reason, moving these directories into their own partitions is a good idea.
</div></div><div class="section" title="5.2. Utilize LUKS Partition Encryption"><div class="titlepage"><div><div><h2 class="title" id="sect-Security_Guide-Secure_Installation-Utilize_LUKS_Partition_Encryption">5.2. Utilize LUKS Partition Encryption</h2></div></div></div><div class="para">
Since Fedora 9, implementation of <a href="http://fedoraproject.org/wiki/Security_Guide/9/LUKSDiskEncryption">Linux Unified Key Setup-on-disk-format</a>(LUKS) encryption has become a lot easier. During the installation process an option to encrypt your partitions will be presented to the user. The user must supply a passphrase that will be the key to unlock the bulk encryption key that will be used to secure the partition's data.
</div></div></div><div xml:lang="en-US" class="chapter" title="Chapter 6. Software Maintenance" lang="en-US"><div class="titlepage"><div><div><h2 class="title" id="chap-Security_Guide-Software_Maintenance">Chapter 6. Software Maintenance</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#sect-Security_Guide-Software_Maintenance-Install_Minimal_Software">6.1. Install Minimal Software</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Software_Maintenance-Plan_and_Configure_Security_Updates">6.2. Plan and Configure Security Updates</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Software_Maintenance-Plan_and_Configure_Security_Updates-Adjusting_Automatic_Updates">6.3. Adjusting Automatic Updates</a></span></dt><dt><span class="section"><a href="#sect-Security_Guide-Software_Maintenance-Install_Signed_Packages_from_Well_Known_Repositories">6.4. Install Signed Packages from Well Known Repositories</a></s
pan></dt></dl></div><div class="para">
Software maintenance is extremely important to maintaining a secure system. It is vital to patch software as soon as it becomes available in order to prevent attackers from using known holes to infiltrate your system.
</div><div class="section" title="6.1. Install Minimal Software"><div class="titlepage"><div><div><h2 class="title" id="sect-Security_Guide-Software_Maintenance-Install_Minimal_Software">6.1. Install Minimal Software</h2></div></div></div><div class="para">
It is best practice to install only the packages you will use because each piece of software on your computer could possibly contain a vulnerability. If you are installing from the DVD media take the opportunity to select exactly what packages you want to install during the installation. When you find you need another package, you can always add it to the system later.
</div></div><div class="section" title="6.2. Plan and Configure Security Updates"><div class="titlepage"><div><div><h2 class="title" id="sect-Security_Guide-Software_Maintenance-Plan_and_Configure_Security_Updates">6.2. Plan and Configure Security Updates</h2></div></div></div><div class="para">
All software contains bugs. Often, these bugs can result in a vulnerability that can expose your system to malicious users. Unpatched systems are a common cause of computer intrusions. You should have a plan to install security patches in a timely manner to close those vulnerabilities so they can not be exploited.
</div><div class="para">
For home users, security updates should be installed as soon as possible. Configuring automatic installation of security updates is one way to avoid having to remember, but does carry a slight risk that something can cause a conflict with your configuration or with other software on the system.
</div><div class="para">
For business or advanced home users, security updates should be tested and schedule for installation. Additional controls will need to be used to protect the system during the time between the patch release and its installation on the system. These controls would depend on the exact vulnerability, but could include additional firewall rules, the use of external firewalls, or changes in software settings.
</div></div><div class="section" title="6.3. Adjusting Automatic Updates"><div class="titlepage"><div><div><h2 class="title" id="sect-Security_Guide-Software_Maintenance-Plan_and_Configure_Security_Updates-Adjusting_Automatic_Updates">6.3. Adjusting Automatic Updates</h2></div></div></div><div class="para">
Fedora is configured to apply all updates on a daily schedule. If you want to change the how your system installs updates you must do so via '''Software Update Preferences'''. You can change the schedule, the type of updates to apply or to notify you of available updates.
</div><div class="para">
In Gnome, you can find controls for your updates at: <code class="code">System -> Preferences -> Software Updates</code>. In KDE it is located at: <code class="code">Applications -> Settings -> Software Updates</code>.
</div></div><div class="section" title="6.4. Install Signed Packages from Well Known Repositories"><div class="titlepage"><div><div><h2 class="title" id="sect-Security_Guide-Software_Maintenance-Install_Signed_Packages_from_Well_Known_Repositories">6.4. Install Signed Packages from Well Known Repositories</h2></div></div></div><div class="para">
Software packages are published through repositories. All well known repositories support package signing. Package signing uses public key technology to prove that the package that was published by the repository has not been changed since the signature was applied. This provides some protection against installing software that may have been maliciously altered after the package was created but before you downloaded it.
</div><div class="para">
Using too many repositories, untrustworthy repositories, or repositories with unsigned packages has a higher risk of introducing malicious or vulnerable code into your system. Use caution when adding repositories to yum/software update.
</div></div></div><div xml:lang="en-US" class="chapter" title="Chapter 7. References" lang="en-US"><div class="titlepage"><div><div><h2 class="title" id="chap-Security_Guide-References">Chapter 7. References</h2></div></div></div><div class="para">
The following references are pointers to additional information that is relevant to SELinux and Fedora but beyond the scope of this guide. Note that due to the rapid development of SELinux, some of this material may only apply to specific releases of Fedora.
</div><div class="variablelist" title="Books" id="vari-Security_Guide-References-Books"><h6>Books</h6><dl><dt><span class="term">SELinux by Example</span></dt><dd><div class="para">
Mayer, MacMillan, and Caplan
</div><div class="para">
Prentice Hall, 2007
</div></dd></dl></div><div class="variablelist" title="Tutorials and Help" id="vari-Security_Guide-References-Tutorials_and_Help"><h6>Tutorials and Help</h6><dl><dt><span class="term">Understanding and Customizing the Apache HTTP SELinux Policy</span></dt><dd><div class="para">
<a href="http://fedora.redhat.com/docs/selinux-apache-fc3/">http://fedora.redhat.com/docs/selinux-apache-fc3/</a>
</div></dd><dt><span class="term">Tutorials and talks from Russell Coker</span></dt><dd><div class="para">
<a href="http://www.coker.com.au/selinux/talks/ibmtu-2004/">http://www.coker.com.au/selinux/talks/ibmtu-2004/</a>
</div></dd><dt><span class="term">Generic Writing SELinux policy HOWTO</span></dt><dd><div class="para">
<a href="http://www.lurking-grue.org/writingselinuxpolicyHOWTO.html">http://www.lurking-grue.org/writingselinuxpolicyHOWTO.html</a>
</div></dd><dt><span class="term">Red Hat Knowledgebase</span></dt><dd><div class="para">
<a href="http://kbase.redhat.com/">http://kbase.redhat.com/</a>
</div></dd></dl></div><div class="variablelist" title="General Information" id="vari-Security_Guide-References-General_Information"><h6>General Information</h6><dl><dt><span class="term">NSA SELinux main website</span></dt><dd><div class="para">
<a href="http://www.nsa.gov/research/selinux/index.shtml">http://www.nsa.gov/selinux/</a>
</div></dd><dt><span class="term">NSA SELinux FAQ</span></dt><dd><div class="para">
<a href="http://www.nsa.gov/research/selinux/faqs.shtml">http://www.nsa.gov/selinux/info/faq.cfm</a>
</div></dd><dt><span class="term">Fedora SELinux FAQ </span></dt><dd><div class="para">
<a href="http://fedora.redhat.com/docs/selinux-faq-fc3/">http://fedora.redhat.com/docs/selinux-faq-fc3/</a>
</div></dd><dt><span class="term">SELinux NSA's Open Source Security Enhanced Linux</span></dt><dd><div class="para">
<a href="http://www.oreilly.com/catalog/selinux/">http://www.oreilly.com/catalog/selinux/</a>
</div></dd></dl></div><div class="variablelist" title="Technology" id="vari-Security_Guide-References-Technology"><h6>Technology</h6><dl><dt><span class="term">An Overview of Object Classes and Permissions</span></dt><dd><div class="para">
<a href="http://www.tresys.com/selinux/obj_perms_help.html">http://www.tresys.com/selinux/obj_perms_help.html</a>
</div></dd><dt><span class="term">Integrating Flexible Support for Security Policies into the Linux Operating System (a history of Flask implementation in Linux)</span></dt><dd><div class="para">
<a href="http://www.nsa.gov/research/_files/selinux/papers/selsymp2005.pdf">http://www.nsa.gov/research/_files/selinux/papers/selsymp2005.pdf</a>
</div></dd><dt><span class="term">Implementing SELinux as a Linux Security Module</span></dt><dd><div class="para">
<a href="http://www.nsa.gov/research/_files/publications/implementing_selinux.pdf">http://www.nsa.gov/research/_files/publications/implementing_selinux.pdf</a>
</div></dd><dt><span class="term">A Security Policy Configuration for the Security-Enhanced Linux</span></dt><dd><div class="para">
<a href="http://www.nsa.gov/research/_files/selinux/papers/policy/policy.shtml">http://www.nsa.gov/research/_files/selinux/papers/policy/policy.shtml</a>
</div></dd></dl></div><div class="variablelist" title="Community" id="vari-Security_Guide-References-Community"><h6>Community</h6><dl><dt><span class="term">Fedora SELinux User Guide</span></dt><dd><div class="para">
<a href="http://docs.fedoraproject.org/selinux-user-guide/">http://docs.fedoraproject.org/selinux-user-guide/</a>
</div></dd><dt><span class="term">Fedora SELinux Managing Confined Services Guide</span></dt><dd><div class="para">
<a href="http://docs.fedoraproject.org/selinux-managing-confined-services-guide/">http://docs.fedoraproject.org/selinux-managing-confined-services-guide/</a>
</div></dd><dt><span class="term">SELinux community page</span></dt><dd><div class="para">
<a href="http://selinux.sourceforge.net">http://selinux.sourceforge.net</a>
</div></dd><dt><span class="term">IRC</span></dt><dd><div class="para">
irc.freenode.net, #selinux, #fedora-selinux, #security
</div></dd></dl></div><div class="variablelist" title="History" id="vari-Security_Guide-References-History"><h6>History</h6><dl><dt><span class="term">Quick history of Flask</span></dt><dd><div class="para">
<a href="http://www.cs.utah.edu/flux/fluke/html/flask.html">http://www.cs.utah.edu/flux/fluke/html/flask.html</a>
</div></dd><dt><span class="term">Full background on Fluke</span></dt><dd><div class="para">
<a href="http://www.cs.utah.edu/flux/fluke/html/index.html">http://www.cs.utah.edu/flux/fluke/html/index.html</a>
</div></dd></dl></div></div></div></body></html>
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