Re: tracking down unidentified users

From: Alan Hadsell (
Date: 11/21/02

From: Alan Hadsell <>
Date: Thu, 21 Nov 2002 02:00:20 GMT

dan sawyer <> writes:

> I have discovered reminants of an attack that apparently took place
> over a year ago. That attack left 4 users in /etc/passwd and
> /etc/shadow. The names are selector1, semaca, tmp, and an altered
> operator profile.
> lastlog indicates these runs are activated the first time after a boot
> when I activate a user as 'root'. I can find no strings relating to
> those names anywhere in the /etc dir.

What do you mean by "activate a user as 'root'?" Are you referring to
logging in as root?

I have seen your posts about this issue in several forums. It appears
that you have a basic confusion between "users" and "jobs" or "runs".

I gather that what you mean is that some process owned by these users
runs whenever you "activate a user as 'root'". The most likely reason
for that is that root's login script is starting the jobs that you

One thing you might consider is finding all files and directories
owned by these users and/or their groups. If there are executable
files owned by these users that have the suid bit set, they will cause
the system to "log in as" that ID when started. From there, they
could launch other processes under that ID.

> What is unique about root from a script and start process then other
> users?

The main thing that's unique about root from that perspective is that
the "init" processes are all started as root, and so unless they take
steps to ensure otherwise, all other processes they start are also run
as root. Of course, root has many other unique aspects, mostly having
to do with privileges it has that other users do not.

As others have done, I urge you not to put the system in question on
the Internet until you have done a reformat and reinstallation of your
operating system to eliminate these issues. You can't ever be sure
that you have fixed them until you do.

Alan Hadsell
If something's already broken, does it really matter how many pieces it's in?
--James Bottomley on lkml

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