Disqus uses its own anti-spam software to smartly combat comment spam. It was designed to learn over time and becomes increasingly accurate with your moderation activity. Spammers are a prolific bunch, and thus there is always some chance that newer techniques may initially get past the anti-spam. These are tips on how to reduce or altogether eliminate spam.
Be sure to mark comments as spam if they are indeed spam. However, be careful not to mark non-spam comments, even if the comments are abusive, offensive, or just plain disagreeable. Marking non-spam comments as spam pollutes the data that Disqus collects and results in less accurate anti-spam detection.
You may mark comments as spam from the Moderation panel, the comment thread itself, and from email notifications.
You may choose to pre-moderate all comments posted on your site. All comments, spam or not, will require moderator approval before being published for others to see. Another option you may want to try is pre-moderating all links in comments. To view and change moderation settings, head to Settings > General > Community Rules.
Blacklists and Whitelists
Disqus offers both Blacklists and Whitelists. After marking comments as spam, you may add the commenter to your blacklist. Alternatively, you could require pre-moderation on all comments and then add trusted commenters to your whitelist.
Decide who is allowed to comment
By controlling who comments on your site, you can prevent spam or other undesirable comments from being posted on your site. You can view these options under Settings > General.