--On July 17, 2006 9:31:50 AM -0400 hchlai@netscape.net wrote:
Hi Snorters,
I have 2 questions regarding sid:1811
/etc/snort/rules/attack-responses.rules:alert tcp $HOME_NET 22 ->
$EXTERNAL_NET any (msg:"ATTACK-RESPONSES successful gobbles ssh exploit
uname"; flow:from_server,established; content:"uname";
reference:bugtraq,5093; reference:cve,2002-0390;
reference:cve,2002-0639; reference:nessus,11031; classtype:misc-attack;
sid:1811; rev:9;
First of all, since ssh sessions are encrypted, I should never see a
packet content of "uname" in non-encrypted format. Am I missing
something fundamental in here or it's just a Monday morning?
Secondly, this signature is recorded in 2 packets by BASE, but neither
packets nor their combine contents contain "uname" in it, so what
exactly triggered this signature? Many thanks!
When investigating the whys and wherefores of a rule's triggering, it's a
good idea to first read the relevant exploit information -
<http://www.securityfocus.com/bid/5093/discuss>
"It is possible for attackers to exploit the vulnerabilities by
constructing a malicious response. As this occurs before the authentication
process completes, it may be exploited by remote attackers without valid
credentials. Successful exploitation may result in the execution of
shellcode or a denial of service."
As I'm sure you are aware, the challenge-response portion occurs before
encryption has taken place, so you would indeed see the characters in the
packet.
Paul Schmehl (pauls@utdallas.edu)
Adjunct Information Security Officer
The University of Texas at Dallas
http://www.utdallas.edu/ir/security/
p7sCZAyYjm8Ww.p7s
Description: S/MIME cryptographic signature
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