5 Free WordPress Plugins to Stop Comment Spam in 2011

One of the unfortunate realities of hosting a WordPress blog is that sooner or later (and probably sooner) you are going to be subject to comment spam — those annoying and often nonsensical blurbs posted as comments to your blog posts. While blogging is a phenomenal SEO tool, those spam comments are anything but.

The vast majority of this comment spam comes from automated bots that scour the internet tossing their obnoxious little ads and links all over your site. However, not all WordPress comment spam comes from bots — a good portion of it actually comes from people who are paid to deliver these meaningless comments throughout the web.

Happily, WordPress has a large community of developers who have been fighting the good fight against comment spam with free plugins that you can easily install on your WordPress blog. There is no single perfect addon that will eliminate all comment spam for you — but by using a combination of two or more anti-spam WordPress plugins you can get pretty close to zero comment spam.

Here are the top 5 free comment spam WordPress plugins to stop comment spam in 2011, along with their pros and cons.

1. Askimet comment spam plugin

Cost: free if your blog is mall enough
Where: Installed to WordPress by default, or download Akimet from WordPress.org. You will then need to get an Askimet key from Askimet.com.

Askimet is a heuristic anti comment spam filter for WordPress blogs. It works by comparing the comment that a user entered to known spam comments. It learns over time which comments are real and which are spam, and automatically puts the spam comments into your queue for moderation.

Askimet gets some fantastic reviews from users and does a shockingly good job at capturing spam into the moderation queue. It does, however, have some downsides. Namely:

  • Comment spam is not actually blocked — instead it is identified and put in the moderation queue for you to deal with.
  • It’s possible for Askimet to mistake real comments for spam comments, and put the legitimate comments into the moderation queue along with all that spam.
  • Finally, Askimet is free only if your blog is small enough and if it’s not for your business. If you’re under 10,000 pageviews in a month and have few enough employees you can use Askimet for free, but once your pageviews go over 10k per month the monthly fee for using askimet climbs fast. I have a fairly popular video game blog, for example (and not a business), and using Akimet as a comment spam plugin would cost me $500/month.

Ultimately Akimet is a great solution that will handle spam for smaller WordPress sites without a large following, but for popular blogs or larger businesses, the costs can add up fast.

2. WP ReCaptcha comment spam plugin

Cost: Free
Where: Download WP ReCaptcha from WordPress.org

Another excellent tool for preventing automated comment spam in WordPress blogs, WP ReCaptcha works by displaying two images that a user must enter before their comment can be posted. The idea here is that bots can’t actually see the images, so they can’t successfully enter the word. In concept recaptcha prevents automated spam entirely. And technically, that may be true.

But, there’s a but.

While recaptcha will block that wholly automated bot spam, it will not protect you from those workers we discussed earlier that are paid to copy and past comment spam all day long. As long as there’s an actual human looking at the image and entering the words, they’ll be able to post whatever they want.

In general WP ReCaptcha is a strong and free plugin for fighting comment spam; however, you really need to use recaptcha in conjunction with another anti-spam plugin, or else you’ll end up spending more time than you should moderating your comments.

3. Cookies for Comments anti-spam plugin

Cost: Free
Where: Download Cookies for Comments from WordPress.org

Cookies for Comment is probably the most appealing WordPress comment spam plugin out there, because of the way it works. Rather than trying to guess what is spam and what isn’t, this plugin creates a cookie that it passes along to the users browser when they load the web page.

Then, if the user tries to comment, the plugin checks and sees if their computer has the cookie.

This is a cunningly effective method because the vast majority of comment spam comes from sources that cannot take cookies — either automated bots, or users posting spam manually but using a custom interface that can’t take the cookies.

This plugin reminds me of the much-lamented WP Spamfree (no longer functional) which used a similar method and, frankly, just downright worked amazingly. The big downside to Cookies for Comments is that it moves the comments flagged as spam over to your moderation queue, where you have to deal with them manually.

For this reason I think Cookies for Comments is best used in conjunction with another plugin that works to prevent spam from getting through in the first place – with WP ReCaptcha, for example.

4. AVH First Defense Against Spam

Cost: Free
Where: Download AVH from WordPress.org

AVH First Defense Against Spam works by comparing the IP address of visitors against known spammer IP addresses. If your commenter is a spammer, they can’t comment — simple enough.

Of course changing or hiding your IP address is easy enough, so again you don’t want to use this addon all by itself. Be sure to have another anti-spam method available on your blog as well.

5. The ultimate protection: require registration

The final and most effective method for preventing automated comment spam is simply to change your WordPress blog settings so that only registered users can post a comment. Since the registration process is more strict (and is yet another step that spammers are unwilling or unable to complete) requiring users to register to your blog before they can comment effectively stops all spam.

You can turn this option on in the Settings > Discussion section of your WordPress admin. Just check the box labeled “Users must be registered and logged in to comment” and you’re done.

Of course the down side of this method is it puts a serious impediment in front of users. Most people on the internet are not going to comment if they have to fill out a form first to register (internet users are inherently lazy).

So while requiring registration is certainly effective, it can also seriously reduce the amount of comments you’ll receive.

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