The sad state of the Internet
It's a real shame that the Internet has deterioted to the point where one security researcher stated in a recent CNet article that "The war to make the Internet safe was lost long ago, and we need to figure out what to do now." And another is quoted as saying "We are losing this war badly," he said. "Even the vendors understand that we are losing the war."
To add to the point VitalSecurity has a link to a short movie that everyone should view in order to get a real grasp on the situation of how easy it is to spam Forums, Blogs, GuestBooks and the like. Wikipedia (the free encyclopedia) has a terrific explanation of this type spam also know as Spamdexing.
I began researching the problem a few weeks ago and what I found is that there is a common denominator to these Spammers. The vast majority try to redirect the user to usually unwanted sites or worse (Trojan.Zlob and Trojan.Codec) ... after a while I began to see a pattern, where the files and sites that were actually doing the redirections were the same few time after time. So I started adding these (about 100) to the HOSTS file, marked with the comment "#[Spamdexing]".
Now this method will not prevent Spamdexing but it will help prevent the users of my HOSTS file from either being redirected to unwanted sites or from getting infected from these culprits.