A blog website may register with a trackback spam filtering service to receive a trackback URL pointed to a computer of the track back spam filtering service. The trackback URL may be posted on the blog to allow readers to trackback to the blog. Trackback pings for linking to the blog may be received by the trackback spam filtering service for evaluation. The trackback spam filtering service may extract comment links from the trackback pings, and provide the comment links to a web reputation service to determine characteristics of the comment links. The trackback spam filtering service may consult a rules database that includes deterministic rules, heuristic rule, or both to determine if a comment link having particular characteristics is pointed to a spammer website. If so, the trackback spam filtering service may block the trackback to the blog.