I am finding an increasing number of blog comments where the user has added what appears to be an innocent and directly related URL in their profile information. Upon clicking on the URL I find that it is redirected to a different URL in a porn site or a shopping site.

If you are going to approve user comments, be sure to test any URLs that users submit to make sure that they are legitimate.

If you are using Akismet, make sure that you click on the Spam link on the Comment approval page to report these mischievous URLs, rather than simply trashing them. On some sites I'm finding about 50% of the comments that make it past Akismet are using redirect links.