Comment spam is the bane of bloggers. Comment spammers are usually bots, although sometimes humans, that scour the Internet in search of blogs with open comment threads upon which to drop irrelevant links and advertising messages. Comment spam is one of the least pleasant tools in the black hat SEO’s tool box.
Moderating comments can be a full-time job for popular bloggers, and anything that takes time away from creating content is leeching revenue from bloggers who depend on their content to bring in advertising revenue or make other conversions.
Sites that are overloaded with spam, and therefore have lots of links to the less salubrious areas of the Internet are also at risk of taking a hit to their SEO. Google uses outgoing links as a signal of a site’s quality, and allowing spammers to infest a site with links to affiliate pages and porn sites is not the best way to get in Google’s good books.
It’s a difficult problem to deal with and even large publishing ventures don’t always manage to keep their comment threads spam-free, but there are a number of methods that WordPress users can employ to reduce the attractiveness of their sites to spammers and automatically throw spammy comments into the penalty box.
Akismet
Most WordPress bloggers should be familiar with Akismet; it’s the most popular spam filtering service available for WordPress. It will prevent spam comments from ever appearing on a site. Akismet is free for personal use and reasonably priced for commercial sites.
Close Old Comment Threads
Spammers like to target old threads because they are less likely to get noticed. In most cases, older articles aren’t going to have ongoing conversations occurring in their comments, so their isn’t much value to keeping comment submissions open.
WordPress makes it easy to close comment threads. You can either do it manually for each post, or you can go to the discussion section under settings in the sidebar menu and specify a time frame for automatically closing them.
Force Commenters To Log In
People and bots are less likely to spam if you force them to jump through a few hoops before they can get their content onto the site. In the conversation settings dialogue, you can configure WordPress to only allow comments from users who are logged in.
A step further is to install a social login plugin, like the one that comes with the JetPack collection. Forcing commenters to login via their social network will reduce spam comments, although it won’t prevent them altogether. It’s fairly easy for spammers to set up fake social media accounts.
Check If Commenters Are Human
Most comment spamming is done by automated bots and there are various methods to verify whether a user is human or not. There’s a pay-off to be made here though. Casual but genuine commenters are also likely to be put-off by having to go to too much effort in order to make a comment. But, in some cases, it’s worthwhile and imposing some friction can also reduce the number of trollish comments as well as spammers.
There are various plugins that will let a WordPress site implement CAPTCHA tests. It’s also possible to have a Turing test which is a bit more fun.
Finally, there are a number of more technically involved ways that a site can combat comment spam. Check out this guide from the WordPress Codex for more details.