Rule: 

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Sid: 
119-1

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Summary: 
This event is generated when the pre-processor http_inspect
detects network traffic that may constitute an attack.

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Impact: 
Unknown. This may be an attempt to evade IDS.

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Detailed Information:
This event indicates that the http_inspect pre-processor has detected
web traffic containing coded ascii values.

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Affected Systems:
	All web servers.

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Attack Scenarios: 
An attacker may try to encode an attack by using the hexadecimal
representation of the ascii characters used in an attempt to evade
detection by IDS.

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Ease of Attack: 
Simple

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False Positives:
These encodings can be relatively prevalent in normal web traffic.

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False Negatives:
None Known.

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Corrective Action:
Check the target host for signs of compromise.

Apply any appropriate vendor supplied patches.

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Contributors:
Daniel Roelker <droelker@sourcefire.com> 
Sourcefire Vulnerability Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:

HTTP IDS Evasions Revisited - Daniel Roelker
http://docs.idsresearch.org/http_ids_evasions.pdf

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