FWIW: The malformed excel rule checks the flowbit xls.download, which is set by
sid:7023, which checks for |D0 CF 11 E0 A1 B1 1A E1|, which is down in Gary
Kessler's magic number list* as a generic Microsoft Office document. "Generic
Microsoft Office document" is congruent with what I've seen.
Kessler's list says Excel documents have |09 08 10 00 00 06 05 00| at a 512
byte offset, and hex editor reviews of Office XP-generated documents seem
consistent with that.
* http://www.garykessler.net/library/file_sigs.html
-----Original Message-----
From: snort-users-bounces@lists.sourceforge.net
[mailto:snort-users-bounces@lists.sourceforge.net] On Behalf Of Joel Esler
Sent: Wednesday, July 09, 2008 10:15 AM
To: Jesper Skou Jensen
Cc: snort-users@lists.sourceforge.net
Subject: Re: [Snort-users] WEB-CLIENT Excel malformed FBI record - False
positive?
Well, that's a separate issue. If you suspect a false positive, please get a
full pcap of the transfer of the traffic, and file it via the false positive
report format you can find on the snort.org website.
J
On Jul 9, 2008, at 5:52 AM, Jesper Skou Jensen wrote:
Jack Pepper wrote:
Check the config file for accuracy, or check that the snort service
is using the same config file that you think it's using.
Joel Esler wrote:
Do you have two HOME_NET lines in your snort.conf file? I'm not
saying anything bad or anything, but it looks like to me that you
have two HOME_NET definitions.
D'oh... You guys were spot on.
It turns out that Debian is just a bit too smart at times... They have
their own config file with a few entries (inluding home_net) that it
uses, instead of those in the snort.conf file.
Thank you guys for spotting this.
It's a bit weird though, that the rule fires at all, because from what
I can gather from the server-logs, there are no Excel files on it,
only Word Documents, and the Word Docuemnt that was downloaded when
this alert fired, is not malicious according to www.virustotal.com so
I doubt there is anything fishy in it.
--
Jesper S. Jensen
Basisnet og Sikkerhed
Uni-C - Ãrhus, Danmark
+45 8937-6666
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[m]
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