Odd, it is.. and yeah, you're right. Ive got over 50,000 alerts for this
rule and the same type of packet.
Best Regards,
Eric S. Hines, GCIA, CISSP
CEO, President, Chairman
Applied Watch Technologies, LLC
--------------------------------------------------
Eric S. Hines, GCIA, CISSP
CEO, President, Chairman
Applied Watch Technologies, LLC
--------------------------------------------------
Email: eric.hines@appliedwatch.com
Address: 1095 Pingree Road
Suite 213
Crystal Lake, IL
60014
Tel: (877) 262-7593 ext:327
Local: (847) 854-5831
Fax: (847) 854-5106
Web: http://www.appliedwatch.com
--------------------------------------------------
Security Management for the Open Source Enterprise
Matt Kettler wrote:
Eric Hines wrote:
All:
SID #: 1893 (SNMP missing community string attempt) sets a depth max of
15 bytes. This signature is improperly firing on several of our networks
as a lot of different devices will set the community string deeper than
15 bytes.
Is this happening frequently enough for everyone else out there to
propose a modification to this rule to have the depth increased or
eliminated, or do you guys consider this to be a local tuning
responsibility of the administrator?
Has anyone else had this problem?
Snort Team: Should we submit this using the Snort signature template for
submitting False Positives? All 50,000 alerts in one day for this
signature were FPs :)
Where do we draw the line on a signature using too tight of a
Depth/Offset, etc.. being a False Positive or User-specific tuning?
----- snip ------
alert UDP $EXTERNAL_NET any -> $HOME_NET 161 (msg:"SNMP missing
community string attempt"; content:"|04 00|"; depth:15;
offset:5;reference:bugtraq,2112; reference:cve,1999-0517;
classtype:misc-attack; sid:1893; rev:4;)
---- example packet -----
0fdd 00a1 0033 d483 3029 0201 0004 0670 .......3..0).....p
7562 6c69 63a0 1c02 0400 a063 f602 0100 0201 ublic......c......
0030 0e30 0c06 082b 0601 0201 0103 0005 00 .0.0...+.........
Erm, call me crazy, but that packet should not have matched that rule, if
the
rule is working correctly. (of course, my brain may be off too, I've not done a
lot of snorting lately)
Note that the rule should fire if "04 00" is found within a range from bytes
5-20 (starting with offset 5, and a maximum depth of 15 bytes from 5).. In this
case, 04 00 is found at bytes 25&26.
The rule shouldn't match.
eric.hines.vcf
Description: Vcard
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