Comment spam refers to comments added to articles or forums online with the sole intention of adding a backlink to a particular website. Comment spam, or forum spam, is commonplace online and is a nuisance to all website owners.
Most blogs and forums will assign nofollow commands to the comment sections of their blogs or forums. This way, if comment spam gets through, at least your site won't pass any authority on to it. However, it's best to banish comment spam from your site altogether as any users reading the comments will likely be put off adding anything relevant to the discussion if it's full of spam.
Using a robust comment system, such as Disqus, weeds out all comments with links in them for you to moderate. You should delete and 'mark as spam' any comments that add anything to the discussion of the topic. If you get a particularly persistent spammer, most systems will allow you to block the user.
Comment spammers often attempt to use flattery to get you to post their link. Don't be duped – the only intention of comment spam is to build links and the commenter will be unlikely to have read the article. In fact, the commenter is more likely to be a robot!
Some black hat link builders use spam bots to post meaningless comment spam to forums and comments across the web. This shady technique is capable of delivering thousands of backlinks to your site in a matter of hours - but it's also likely to do more harm than good. Generating such a large number of links quickly will be likely to send a danger signal to the search engines. If an SEO service ever offers to get you thousands of backlinks in this way, kindly decline (and look for someone else to do your digital marketing).