Rule: 

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Sid: 
111-14

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Summary: 
This event is generated when the pre-processor stream4
detects network traffic that may constitute an attack.

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

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Detailed Information:
This event indicates that the pre-processor stream4 has detected forward
overlapping packets that may indicate an attempt is being made to evade
detection by an IDS.

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Affected Systems:
	All systems

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Attack Scenarios: 
An attacker can attempt to hide malicious payload data by sending
fragmented packets that overlap.

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Ease of Attack: 
Simple. Tools such as fragroute contain this functionality.

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False Positives:
None Known.

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False Negatives:
None Known.

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

Ensure the system is up to date with any appropriate vendor supplied patches.

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Contributors:
Martin Roesch <roesch@sourcefire.com>
Sourcefire Vulnerability Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:

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