Rule:

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Sid:
2452

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Summary:
This event is generated when a host in your network that has Yahoo Instant Messenger running attempts to maintain contact with a Yahoo IM server.

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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:
Hosts running Yahoo IM periodically communicate with a Yahoo IM server to maintain their connection.  This is a keep-alive message that simply indicates the presences of a host running Yahoo IM.

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Affected Systems:
Any host running Yahoo Instant Messenger.

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Attack Scenarios:
This particular type of Yahoo IM exchange has no known attacks, however it may represent a policy violation because the host is running Yahoo IM.

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Ease of Attack:
A host running Yahoo IM will automatically ping a Yahoo IM server.

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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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