unix question: unknown user logged in? hacked?

[Mike Wright]

Hi all,

There is a mystery user on a remote system that I can't identify.  I 
want to be sure that it's not an uninvited guest :(  If anybody is 
willing to help I'd be most aprpreciative.

Running fc6, but I don't thinks it's relevant, although it may be.

The box is at a remote location and I access it via ssh.  When I run 
"top" it shows 2 users, but when I run "who" it shows only one, me, from 
my remote location.

At first I thought it might have been a left open login on one of the 
mingetty's so I disabled them all in inittab and changed runlevels from 
3 to 4 and saw that all the mingetty's were gone (I think that should 
logout anybody on one of those), then returned to runlevel 3 and re-ran 
"top".  Still 2 users.

I don't think it can be anybody left over from a previous runlevel 5.

I ran "ps auxf" and went over it line by line and couldn't find any 
other bash sessions than my current remote login on pts/0.

Anybody know how to identify the second user shown by top?

I'm very paranoid about hackers/owners/skiddies and this definitely has 
my ears perked up.

Thanks in advance for any tips or ideas,
Mike Wright :m)