Rule:  
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Sid:
1139

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Summary:
This event is generated when an attempt is made to evade an IDS in a 
possible web attack by sending an obfuscated request.

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Impact:
Unknown.

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Detailed Information:
Some CGI attacks can be accomplished by using HEAD instead of GET.
Additionally, some web servers will interpret "/./" as simply "/".
An attacker might try to combine these methods in an attempt to
obfuscate an attack or during the reconnaissance phase of a penetration
attempt in order to bypass an IDS.

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Affected Systems:
	All Web Servers.
 
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Attack Scenarios:
An attacker may use an automated tool, like Whisker, to obfuscate an
attack.

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Ease of Attack:
Simple. Exploit scripts and tools are widely available.

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False Positives:
None Known

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False Negatives:
None Known

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Corrective Action:
Examine the host for signs of compromise.

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Contributors:
Original rule writer unknown
Original document author unkown
Sourcefire Vulnerability Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:

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