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Rule:
--
Sid:
119-5
--
Summary:
This event is generated when the pre-processor http_inspect
detects network traffic that may constitute an attack.
--
Impact:
Unknown. This may be an attempt to obfuscate an attack an evade an IDS.
--
Detailed Information:
This event is generated when the pre-processor http_inspect detects
base36 encoded characters in a web request. This may be used in an
attempt to obfuscate an attack against a webserver or to evade an IDS.
--
Affected Systems:
Microsoft IIS web servers (Asian)
--
Attack Scenarios:
An attacker need only encode a web request using base 36 encoding.
--
Ease of Attack:
Simple. Exploits exist
--
False Positives:
None Known.
--
False Negatives:
None Known.
--
Corrective Action:
Check the target host for signs of compromise.
Apply any appropriate vendor supplied patches.
--
Contributors:
Daniel Roelker <droelker@sourcefire.com>
Sourcefire Vulnerability Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>
--
Additional References:
HTTP IDS Evasions Revisited - Daniel Roelker
http://docs.idsresearch.org/http_ids_evasions.pdf
--
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