If you run a forum, you've probably run into this problem before: users who register accounts and use them to make posts that promote their own products or services, dropping links like they're going out of style. That's called link spam, and it is sometimes used to raise a site in the SERPs. This article will tell you how to combat at least some of it.
This came to my attention via Michael Martinez, who wrote about it in his SEO Theory and Analysis blog. He was complaining about “faux SEOs who run link spamming communities.” According to Martinez, these would-be SEOs simply “sell, share, or recommend link spamming robots that create fake user accounts and profiles on blogs and forums for the sake of 'link building.'”
The link building software builds profiles on tons of communities, and each profile page links back to the website that the software's user is trying to raise in the SERPs. I'm not familiar with the software myself, but presumably at least some types can also be used to make posts with links in forums. This is ten times of icky, for at least two reasons. One, it dirties up a perfectly good forum, making it an unpleasant place for the members and adding massively to the workloads of moderators and administrators. And two, it's wasted effort! As I understand it, Google has devalued forum-based links to the point that they're not worth the time to pursue even if you automate the process.
If you're reading SEO Chat, you're probably a savvy enough SEO to know this already. But if you run a forum or a blog, you may be pulling out your hair over spammers who either don't know or don't care (or both). How do you fight them? Martinez offers some advice for those who are specifically dealing with spam from Backlinksforum.com, but some of it can be generalized.
First, delete all user accounts with profiles that link back to backlinksforum.com, a notorious spammy link builder. I'd further generalize this: when you find other spammers on your site, check to see where their member profile links to, and add that link to a “black list.” If you can set it up, automatically delete any profile that links to a site on the black list.
Second, do NOT permit search engine crawlers to index your member profile pages. You can do this by modifying your robots.txt file. This prevents spammy links in profile pages from being spotted by the search engines, which deprives spammers of what they're looking for in the first place.
Third, make it harder for anyone but a human to register a profile. That means turn on everything: CAPTCHA, email confirmation, the works. If you give the robots a hard enough time, you'll presumably get fewer of them making it all the way through the process.
Fourth, take advantage of the software's shortcomings. It puts the word “man” (short for “manual”) into any field it doesn't know how to fill out, like “Interests.” So if a user profile includes the word “man” in a strange field, that profile might have been created with automated software.
Fifth, delete any user account that hasn't been confirmed after one day. That's why you activated everything; robots can't confirm accounts.
These tips may not catch everything. Martinez seemed to see some indications that certain types of automated software accommodate “some level of user interaction.” But following the steps in this article can help you to make your forums and blogs a much more pleasant place, thus encouraging the kind of traffic you REALLY want.
Search Optimization 
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