fedora 8 hacked?

[tom lee]

Hello,
I used fedora 8 with ssh and sendmail port open only. OS has the
latest update with selinux enforced.
sendmail is the latest 8.14.2.

my machine was mounted as rw for directory "/", it works fine for a
while for sending out emails.
then I find the machine was changed to mount as read only for
directory "/". I cannot create any files in the directory / including
/tmp, nor can I send out emails of course. it complains the file
system is read-only. running "mount" command shows the machine is
mounted as "rw".  I checked no more log files modified any more under
/var/log directory. reboot the machine, the problem is gone.

any possible the machine got hacked or is there a way to check what
caused this problem?

thanks in advance.