Re: [Full-disclosure] Microsoft GhostBuster Opinions
From: Dave King (davefd_at_davewking.com)
Date: Fri, 18 Mar 2005 08:39:58 -0700 To: email@example.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.
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.
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