Rule:

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Sid:
2458

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Summary:
This event is generated when a host in your network that has Yahoo Instant Messenger running has joined a chat room or is examining chat rooms to join.

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Impact:
Possible policy violation.  Instant Messenger programs may not be appropriate in certain network environments.

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Detailed Information:
Yahoo IM provides a means of allowing users who share similar interests to join a chat room and exchange messages.  While there are no known exploits associated with exchanging messages, this type of activity may not be appropriate in certain network environments.  

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Affected Systems:
Any host running Yahoo Instant Messenger.

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Attack Scenarios:
No known attacks.

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Ease of Attack:
No known attacks.

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False Positives:
None Known.

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False Negatives:
It may be possible for Yahoo IM traffic to use other ports than the default expected ones.  

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Corrective Action:
Disallow the use of IM clients on the protected network and enforce or implement an organization wide policy on the use of IM clients.

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Contributors:
Sourcefire Research Team
Judy Novak <judy.novak@sourcefire.com>
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Additional References:
Yahoo Protocol
http://www.cse.iitb.ac.in/~varunk/YahooProtocol.htm

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