Re: Microsoft GhostBuster Opinions

[Dave King <davefd () davewking com>]

Ron DuFresne wrote:

> If the kernel is modified, on a windows or *nix system, you are going to
> have a clear clue upfront;  the system will have rebooted.  Course, a
> failing system that reboots or blue screens every few weeks rather then
> runs stable unless there is a total power outage or a maint window when such
> things are done is another problem altogether...
>
> Of course, I'm not sure you understand what tripwire is or does, further
> research might be in order.
>
> Thanks,
>
> Ron DuFresne
>  

   I don't agree that a system reboot is a  reliable way to know that 
you have a rootkit.  I think anyone who's used Windows enough will agree 
that blue screens are also not a realizable way to determine if you've 
got a rootkit.  It doesn't make sense to me to format and reinstall  
every Windows machine that restarts itself at an odd time.  However, 
both of these can be signs to tip you off that you should  run some 
tests and see what you can find.  Like I said, GhostBuster could 
possibly be one tool to help with this.

   About Tripwire, I understand what it does.  It basically runs a file 
integrity check on certain files and reports the differences from the 
last (hopefully known good) scan.  Say that Tripwire is running on a 
system that's been compromised by a rootkit that's been designed to 
evade file integrity checkers such as tripwire.  Since the rootkit has 
control of the kernel it has control of all the low level functions, 
like returning a file when asked for one.  So one way to evade tripwire 
would be to return the real file when asked for it in read-only mode and 
return the rootkit file when asked for it in execution mode.  That way 
tripwire won't think the file has changed, since it's being given the 
same file as it checked before, but when the file is executed then it's 
the malicious file.

Laters,
Dave King
http://www.thesecure.net


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