Rule: 

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Sid: 
129-2

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Summary: 
This event is generated when the pre-processor stream5 detects network traffic that may constitute an attack.

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Impact: 
Unknown.

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Detailed Information:
This event indicates that the pre-processor stream5 has detected a packet with only the SYN flag set that contains a payload. A packet with this flag set is meant to only set up a session between a client and server. Any data in a packet of this kind indicates malicious activity is taking place.

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Affected Systems:
All systems

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Attack Scenarios: 
An attacker can attempt to evade an IDS by sending a malicious payload in a packet designed to set up a session.

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Ease of Attack: 
Moderate.

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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:
Steven Sturges <ssturges@sourcefire.com>
Sourcefire Vulnerability Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:

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