Signal Spam provides email and web client tools to allow you to submit spam emails you have received. These spam emails are then analysed, categorised and added to a database of known abuse. ISP's can subscribe to this database for free to help filter out and block spam.
It allows you to filter and search for spammer comments on your channel and other's channel(s) in many different ways AND delete/report them all at once (see features below).
Say Goodbye to comment spam on your WordPress blog or website. Antispam Bee blocks spam comments and trackbacks effectively, without captchas and without sending personal information to third party services. It is free of charge, ad-free and 100% GDPR compliant.
Anti-Spam Features. CleanTalk protects your website from spam bots and spam in Comments, Orders, Widgets, Registrations, Bookings, And any custom web form, Contact Emails, Subscriptions, Checks the existing comments and users for spam.
Akismet checks your comments and contact form submissions against our global database of spam to prevent your site from publishing malicious content. You can review the comment spam it catches on your blog’s “Comments” admin screen.
Mollom is a freemium web service to get rid of spam, unwanted content and fake users on your Drupal, Wordpress and Joomla site or blog.Discontinued
"The Mollom content moderation service is no longer available … as of 2 April 2018."
Web Form SPAM Protection enables you to encrypt information on HTML forms and protect yourself from SPAM. Web Form SPAM Protection has been designed to be simple. It doesnt require PHP or ASP support so you dont need any programming knowledge or skills.