intrusion detection

[David Bernier <david250@videotron.ca>]

Dear Debian users,

I think my computer was hacked.  A music CD that I bought in a store 
(Redbook audio
standard) was left in the CD/DVD bay.  Then, mysteriously, a song
by Destiny's Child ("Jumpin' Jumpin' ") got transformed into the *.ogg 
format, but
I didn't ask for that.  Same sound from stereo playing Redbook format 
audio CD
and the *.ogg file on the hard drive ...

So I took a test-drive of Ubuntu 8.04 Live CD, and then did a complete
reinstall.  Now, I'm using Ubuntu and  the firestarter firewall.

I'd like to know about ideas for security, including for example 
intrusion-detection systems.

Thanks,

David Bernier