Show HN: Replacing CAPTCHAs with adaptive proof-of-work in WordPress

A WordPress plugin called 'adaptive proof-of-work' has been created to replace CAPTCHAs and block spam bots. The plugin, which is free and open-source, uses a proof-of-work approach to block spam by requiring spammers to perform a calculation effort for each post. This makes it expensive for spammers to post large amounts of spam, allowing only targeted high-quality approaches. The plugin has been installed on over 4000 active WordPress instances and works with most webforms and plugins. It uses pattern recognition on the HTTP-post level and can be enhanced with custom patterns. The plugin is licensed under GPL-2.0 and can be previewed directly on WordPress.org.