Hacked or not ?

[Lupe Christoph]

On Saturday, 2004-06-12 at 13:15:33 +0200, Peter Rosa wrote:

> please advice me - I was on holidays for one week. After return I found in
> security mails from router (chkrootkit) following message:
> Checking `lkm'... You have     1 process hidden for readdir command
> You have     1 process hidden for ps command
> Warning: Possible LKM Trojan installed

> It apeared only onece. From previous and next days reports, the message is
> not present.

This is an artifact. chkrootkit uses two methods to look at the running
processes - ps and /proc. When a process terminates between the two
runs, you will get this. I see it at irregular intervals on all my
machines that run chkrootkit.

But if your machine is critical, running chkrootkit once daily is not
enough. This gives a cracker too much time to nest in. Run it at least
every hour.

Are you running an integrity checker like AIDE, Tripwire, etc?

> How could I be sure, the machine is not hacked ?

You can't. Not in general. chkrootkit goes only so far. Always assume
the worst. But don't panick.

HTH,
Lupe Christoph

PS: Flames that this is not a security help mailing list to /dev/null,
    please. If you want to flame me, put the energy into creating a
    freebsd-security-help mailing list instead.
-- 
| lupe at lupe-christoph.de       |           http://www.lupe-christoph.de/ |
| "... putting a mail server on the Internet without filtering is like   |
| covering yourself with barbecue sauce and breaking into the Charity    |
| Home for Badgers with Rabies.                            Michael Lucas |