SecurityFocus reports at http://online.securityfocus.com/archive/1/257584 a series of security problems affecting the correct functioning of Yahoo Messenger version 5. This version of Yahoo Messenger listens on port 5101 of the client computer, which creates a series of problems that could be exploited by an attacker that sends traffic to the aforementioned port in the targeted user's computer. More precisely, an attacker could perform the following actions on the affected system: -Carry out a denial of service attack on Yahoo Messenger by overflowing the message field in the yahoo protocol. Similar effects can be caused by overflowing the Imvironment field. -Send messages under another name, impersonating a sender. -Send multiple messages from different names, flooding a certain user with messages and overloading their client. -Add a person to their list of contacts (without the person's consent) and send messages to them until the person's IP address is sent in a message over Yahoo's server.