Actually this is old news, see this post from messenger-blog.com by TB:
quote:
When sending malicious links in group conversations, like .pif, the MSN server will not just discard the message, nor will it boot you off the conversation. Instead, it will end the conversation, kicking everyone off, not just you! Using this method, anyone can easily disband a group conversation by just typing “.pif”. And this is not all, the best part of this all is that noone will be able to tell who disrupted the conversation!
http://www.messenger-blog.com/?p=146
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