GEN:SID 1:2451
Message CHAT Yahoo IM voicechat
Summary This event is generated when a user in your network has successfully registered with a Yahoo Instant Messenger server to receive voice chat messages or is receiving voice chat messages.
Impact Possible policy violation.  Instant Messenger programs may not be appropriate in certain network environments.
Detailed Information Yahoo IM voice chat allows IM users to exchange audio messages.  This activity may not be appropriate in a corporate environment.
Affected Systems Any host running Yahoo Instant Messenger.
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.
Ease of Attack Easy to exchange voice messages.
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.
Additional References Yahoo Protocol
http://www.cse.iitb.ac.in/~varunk/YahooProtocol.htm