-----Original
Message-----
From:
[EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]] On Behalf Of Matt
Sent: Tuesday,
January 31, 2006 4:50
PM
To:
[email protected]
Subject:
[Declude.Virus] Encoded viruses...worried
Someone just reported to me
that MyWife.d (McAfee)/Kapser.A (F-Prot)/Blackmal.E (Symantec)/etc.,
has a 3rd of the month payload that will overwrite a bunch of files.
It's really nasty. More can be found at these links:
http://isc.sans.org/diary.php?storyid=1067
http://vil.nai.com/vil/content/v_138027.htm
This started hitting my system on the 17th, possibly seeded through
Yahoo! Groups. The problem is that it often sent encoded attachments
in BinHex (BHX, HQX), Base64 (B64), Uuencode (UU, UUE), and MIME (MIM,
MME), and I'm not sure that Declude is decoding all of these to see
what is inside. For instance, I found that some BHX files that clearly
contained an executable payload, showed up in my Virus logs like so:
01/16/2006
05:36:49 Q7741EFB6011C4F95 MIME file: [text/html][7bit; Length=1953
Checksum=154023]
01/16/2006 05:36:50 Q7741EFB6011C4F95 MIME file: Attachments001.BHX
[base64; Length=134042 Checksum=8624521]
There was no mention about the
payload inside of it, and there almost definitely was. The same
attachment name with the same length was repeatedly detected as a virus
later on that day. This likely was a PIF file inside, though it could
also have been a JPG according the notes on this virus. I, like most
of us here, don't allow PIF's to be sent through our system, but when
the PIF is encoded in at least BinHex format, it gets past this type of
protection.
Here's the conundrum. This mechanism could be exploited just like the
Zip files were by the Sober writers and continually seeded, but instead
of requiring some of us to at least temporarily block Zips with
executables inside, an outbreak of continually seeded variants with
executables within one of these standard encoding mechanisms would
cause us to have to block all such encodings. I therefore think it
would be prudent for Declude to support banned extensions within any of
these encoding mechanisms if it doesn't already. I readily admit that
this could be a lot of work, but it could be very bad if this mechanism
becomes more common. This particular virus is so destructive that a
single copy could cause severe damage to one's enterprise. I cross my
fingers hoping that none of this would be necessary, but that's not
enough to be safe.
Matt
