Security Incidents mailing list archives

Re: strange windows behaviour.


From: J Mike Rollins <rollins () wfu edu>
Date: Fri, 10 Oct 2003 11:49:33 -0400 (EDT)


The rundll32 path\to\the\trojan.dll,Uninstall does seem to remove the
entries from the registry.  However, the stream is still on the system.
Something like, "echo A > C:\path\to:trojan.dll" will clobber it.

A comment on how to un-install this is in the comments of the program.
Along with a bunch of other interesting text.
I have posted the strings from the trojan on a web page:

        http://www.wfu.edu/~rollins/trojan.txt

However, I am not sure that I feel safe after un-installing it this way.
If this is a backdoor program, who knows what else might have been done to
the system.


On Fri, 10 Oct 2003, Fabio Panigatti wrote:

On September 25, 2003, I posted an article "Analysis of a Spam Trojan"
to the full-disclosure and focus-virus Listservs. It details one
particular spam trojan we found at the University of Minnesota. The
full-disclosure archive can be viewed at:
http://lists.netsys.com/pipermail/full-disclosure/2003-September/010914.html

I went through the same analysis a couple of weeks ago and I can confirm
a lot of your findings about this trojan, formerly known as AFlooder.

The infection way was a VBScript script embedded in the html code of
a spamvertized web page with mime type application/hta. The vbscript
exploits the Scripting.FileSystemObject vulnerability of IE to write
the file audio.exe in the local filesystem, and then runs it whith a
Shell.Run. Audio.exe creates two files, one exe and one dll, in the
system folder, with casual names. The exe is then referenced in one
or more "autorun" keys of the registry. When the exe is fired up, it
loads the dll in the execution space of explorer process and then it
dies. The actual trojan is the dll, which is invisible in the task
list because is running like an explorer.exe subprocess, eluding some
personal firewall or a cursory analisys of the system.

For the ones who are in trouble in removing the trojan, seems that the
trojan can be uninstalled with "rundll32 path\to\the\trojan.dll,Uninstall",
but I suggest to eradicate it with plain old manual methods, swithcing to
DOS mode and deleting the involved files and registry keys. Where a DOS
mode isn't available, the [rename] section in wininit.ini may helps a lot.
In winnt/2k use InUse.exe, from the reskit, as administrator.


Fabio


Mike

    Network Operations and Security, Wake Forest University
======================================================================
          J. Mike Rollins              rollins () wfu edu
     Wake Forest University     http://www.wfu.edu/~rollins
        Winston-Salem, NC            work: (336) 758-1938
======================================================================


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