Before going into the practicalities, you should understand how and why spam comments appear in the first place.
Typically, spam comments are part of someone’s poor SEO strategy aimed at getting as many links as possible (which isn’t the answer to higher rankings!).
Most spam comments are not posted manually, but with a help of special spamming software.
If your blog posts are open for comments, sooner or later you’ll experience comment spam. As your blog grows, comment spam becomes a daily hassle. If a comment looks more like an unsolicited advertisement, it’s probably spam.
There are a few ways to combat spam comments:
Enable comment moderation
Start by configuring WordPress to send all comments to moderation (which means every comment will be emailed to you for approval before it gets published on your site). You can do this by navigating to your Settings and then Discussion on your Dashboard.
Turn off trackbacks
A trackback is a notification that someone else has linked to one of your posts. Picture a trackback as a conversation that links two blog posts together. To turn them off, go to Settings > Discussion > Default Article Settings, and uncheck “Allow link notifications from other blogs (pingbacks and trackbacks).”
Automatically close comments after 30 to 60 days on all your posts
You will get most of your valid comments during the first few weeks after you publish a post. To close comments on every post after a specified number of days, go to Settings > Discussion > Other Comment Settings. Check the box next to “Automatically close comments on articles older than” and choose 30 or 60 days in the selection box.
This allows you to clean your moderation queue by creating a blacklist of spammy words, websites and IP addresses. Browse through the past spam comments and add all the IP’s and common spammy words to the box.
Our favourite spam protection service for WordPress, that filters all the comments for you without any additional settings needed!