Re: [linux-security] Re: Re: Checking remote servers

[Dave <dgriffi ultrix6 cs csubak edu>]

On Sat, 16 May 1998, PaZeN wrote:

> The best and easiest way to Admin Remote Servers is to connect via a
> call-back system and admin it using telco lines.  Then you would have
> relitively little chance of being attacked via the internet, and all but
> the best system crackers know how to subvert call-back (those you can't
> stop anyways).  There is a cheaper/easier way to change a write
> protected filesystem.  This is to use a ZIP/Jaz disk from iomega
> (www.iomega.com).  With these disks you can write protect the disk using
> a password.  That is what I would do. 

1)  Single-modem callbacks are notoriously insecure.  Just feed a dialtone
down the line when you're ready to hang up and be called back.  Most
modems won't actually hang up when you do this.  Double-modem callbacks
can be subverted with a bit of call-forwarding.  What you're doing here is
assigning trust based on your entry via an obscure door, yet unguarded
door.  Instead, you may wish to use a pair of point-to-point encryption
boxes and use a good modem that can accept a password.

[mod: Yeah, if you have such crappy software, you deserve to be
hacked: your software should MAKE VERY SURE that indeed the line is
given up, even if the other side pulls tricks on you. (Drop DTR should
make the modem hangup. Always.) Can you do call-forwarding from a
DIFFERENT line in the states? Not here. -- REW]


2)  Because Zip and Jaz drives are write-protected through software, an
intruder can easily flip the write-protection off once he has root access. 
You should be using a 3.5" MO drive or hard drive with the write-protect
jumper engaged.

[mod: This is the firmware in the drive right? Can you subvert that
from the host end? --REW]

--
David Griffith
dgriffi ultrix6 cs csubak edu