WordPress has many built-in tools that can help reduce comment spam but they are rarely used as they require manual intervention. This being said while plugins like Askimet are useful they do add an overhead (while very little) and they are not always the most effective tool.
By utilizing WordPress and a custom comment blacklist you can reduce the total number of comments that are not caught by Askimet. In order to make use of this feature go into your WordPress admin panel. Go into your settings window and into the discussion settings.
Under the discussion settings there are two areas for your comment blacklist and while they function very similarly they actually do two very different things.
Comment Moderation allows you to set rule sets of words, names, url’s, emails or IP addresses in order to block spammers. That being said the rules will also match inside words meaning “press” will match WordPress. Comments that are caught by this rule set will always be sent to your moderation queue meaning you will be able to look at and manually approve their acceptance or not.
Comment Blacklist allows you to set rule sets of words, names, url’s, emails or IP addresses in order to block spammers. That being said the rules will also match inside words meaning “press” will match WordPress. The difference is Blacklist will automatically send any comment caught by those rules into the trash as opposed to the comment moderation queue.
There are many different outlets to find reliable filters for this section. But instead of writing your own there is a readily available filter already out there on GitHub that has 24,000+ entries.
Simply copy and paste these into the Comment Moderation window and spam will automatically be moved to your moderation area.