What is Akismet?

Akismet is a very well known anti-spam plugin for WordPress created and maintained by the folks at Automattic (the developers of WordPress.com). The plugin was created to allow bloggers and site owners to quickly protect their comments from spam without having to manually approve each comment before publishing. According to WordPress.com's official website, Akismet is by far their most successful and popular product. When you install the plugin and activate it on your blog and site, all your user comments are scanned with an anti-spam algorithm that consists of a black list (text patterns used to filter spam) and a white list (words from which to build whitelists). The best thing about the service is that it does not just stop at just checking for spam but it also helps you catch comment/email spoofing as well as trackbacks originating from illegal sites or spammers sites hosting malicious scripts.

Akismet is used by over 5+ million blogs and websites to protect the comments on their sites against spam.

Akismet was created by Matt Mullenweg in the year of 2005.

Features & Functionality

Automatically checks comments and filter: It automatically checks all comments before they are posted to your blog/site and filters out spam. Checks comments for: Spam, comment or link duplication, sites with malicious scripts and email spoofing.
Highly customizable: You can customize the Akismet plugin settings according to your preference in the WordPress admin area. You can even disable the default Akismet's settings and customize it according to your preference.
Manual Spam Filter: It allows you to manually check and approve or delete comments, trackbacks as well as pings by entering your admin area of your site/blog.
Extensive API support: If you are into plugins development, the Akismet plugin provides an excellent Akismet API that allows other plugins to check comments/trackbacks against the Akismet service. Comment status history: It allows you to view the status history of either approved or rejected comments with time stamps.
Bad Urls in Comments: If the URL of a comment is found to be pointing to an invalid resource, it will get caught by Akismet as spam. With this feature, Akismet helps you avoid broken links in comments on your site which may lead to further spam or malicious links.