Definition
Comment spam is a Black Hat SEO technique that involves mass-posting comments on blogs, forums, and community sites to obtain backlinks. This practice can be manual or automated using tools like ScrapeBox, GSA Search Engine Ranker, or Xrumer. Spammy comments are typically generic ('Great article, thanks!'), off-topic, and contain a link in the URL field or comment body. Although most comment links have been nofollow since 2005, this practice persists because some sites don't apply nofollow and the sheer volume can still have an impact. Google can penalize sites that engage in comment spam and sites that don't moderate their comments. Best practices include: enabling comment moderation, using anti-spam tools (Akismet, reCAPTCHA), applying nofollow/ugc on comment links, and disabling comments on old posts.
Key Points
- Black Hat technique involving mass-posting links in comments
- Most comment links have been nofollow since 2005
- Can trigger penalties for both the spammer and the unmoderated site
Practical Examples
Automated comment spam attack
A WordPress blog receives 500 spam comments overnight, all containing links to pharma sites. The owner activates Akismet and reCAPTCHA, deletes the spam, and adds the ugc attribute to all comment links.
Outgoing spam penalty
An unmoderated forum accumulates thousands of spam comments with toxic links. Google applies a 'User-generated spam' manual action.
Frequently Asked Questions
Very minimal. Nearly all modern CMS platforms apply nofollow or ugc to comment links. The risk/reward ratio is largely unfavorable.
Enable an anti-spam plugin (Akismet for WordPress), add a reCAPTCHA or honeypot, enable manual comment moderation, close comments on posts older than 90 days.
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Last updated: 2026-02-07