[CentOS] AIDE or OSSEC on CentOS 5.4 x86_64?

David McGuffey davidmcguffey at verizon.net
Sun Nov 29 23:52:14 UTC 2009

On Sun, 2009-11-29 at 20:31 +0000, John Horne wrote:
> On Sat, 2009-11-28 at 18:57 -0500, David McGuffey wrote:
> > Starting with a fresh load and after I finish hardening the load
> > following the Center for Internet Security (CIS) guidance, I'm wondering
> > whether AIDE or OSSEC would be a better intrusion detection system.
> > 
> > I installed AIDE and did a quick test of AIDE and after initializing the
> > db and applying the recent cups update, I found that 1700+ files had
> > changed.  Those are a lot of changes to wade through to determine if
> > they are legit or not. If that is all that AIDE can do, then it is not
> > "manageable."
> > 
> > Seems to me that any IDS must be tied to the yum update process so that
> > one is not dealing with hundreds/thousands of changes that were brought
> > in by a yum update that I choose to apply.
> > 
> > Is OSSEC any less noisy?
> > 
> More so as far as I can tell.
> Don't forget that prelinking will cause files to regularly change their
> hash value whether they have been updated or not. Aide does have a patch
> to cater for prelinking (as far as I know it is not in the current
> release so you'll have to search their archives for it). OSSEC does not
> know about prelinking, so will frequently report files having changed.
> Shameless plug: You could take a look at rootkit hunter
> (http://sourceforge.net/projects/rkhunter/), its file properties testof
> knows about prelinking and can use the local RPM database to verify
> files, so an updated file won't be flagged as having changed unless
> someone has deliberately changed it.
> Another alternative is Samhain. As far as I remember it can handle
> prelinking, but will report updated files as having been changed.


I'm not looking for a "tech" solution so I can sit on my butt and let
the tools do their magic.  What bothered me was that I did the install,
configured the load the way I wanted it, ran AIDE to init the db.  A
couple of days later, the CentOS list informed us that cups needed to be
updated.  I did the update and immediately ran AIDE to see what changed.
That cups update changed nearly 1,700 files.  

That caused me to think...there should be a way to tie the IDS to the
patching (that I deliberately authorized), so that the changes related
to the patching are either ignored, or collected at the end of the
report under the header something like:

"The following changes appear to be tied to authorized patching
activity...if you did not authorize these changes, then find out why
they changed..."

I still want to see the changes, but it would be nice to see the ones I
authorized through the update service to be partitioned off from the
ones that seem to have no reasonable explanation.


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