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Re: secure installation

Rick Moen <rick@linuxmafia.com> writes:

> And this is _another_ reason why a properly targeted file-based IDS is a
> really capital idea -- as is alertness about what is and is not aberrant
> system behaviour.  I can even make this point in a Debian-relevant way.
> All hail to the Debian Project's sysadmins, who in November 2003 showed
> everyone how to do it right:  http://linuxgazette.net/issue98/moen.html

Yup.  IDS systems are wonderful.  But they do require discipline.  I've
seen a depressing number of people deploy an IDS and then never bother to
update the database.  When you have >1MB of changes reported every day
that you've trained yourself to ignore, you're just wasting CPU.

That's really the take-home point with all of these discussions.  There
are a lot of great security tools available if you're paying attention and
really think about what you're doing, clear anomalies, and make sure that
everything they report really *is* unusual.  If you don't do those things,
and most unskilled users won't, then it's all about the defaults.  If the
defaults don't get it right, it's pretty much a lost cause.

This is, for example, one of the reasons why I think Debian's logcheck
package is such a good idea.  It scans your system logs and mails you
anomalies, and *lots of Debian developers use it and submit patches to
filter out all the expected output*.  The latter is vital.  Because clued
Debian users and developers keep the rule set up to date, it's actually
usable for someone who doesn't know what they're doing since the reports
aren't full of noise that isn't actually a problem.  (It could, of course,
be better, but I think it's quite good already.)  Of course, even a good
log checking program isn't as good as an IDS with a database in secure
media (I personally use network file systems with strong ACLs requiring
separate authentication; it's not ideal, but it requires a sophisticated
attacker to compromise) since many attackers immediately wipe out the
logs.  logcheck is probably more useful for catching hardware failure than
for catching security, although it can pick up security-related problems
(such as piles of ssh password cracking attempts that remind you that you
forgot to add an iptables rule for ssh).

Russ Allbery (rra@debian.org)               <http://www.eyrie.org/~eagle/>

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