The original PopStopper from PanicWare.com does stop Messenger spam but only the professional paid for version. The free one doesn't but I'm sure there are some out there that do. The Messenger service was built by Microsoft and was intended for use by network administrators in a business environment. It allowed them to send internal messages to network users without the hassle of email. Unfortunately it wasn't particularly difficult for anyone to use and that's why we see so much garbage appearing on our screens. It is of no use whatsoever for those of us using our PC's at home, so close it down.