This (or something very similar) is a core feature of phpBB: https://www.phpbb.com/support/docs/en/3.2/kb/article/how-to-configure-q%2Ba-captcha/ https://www.p

This (or something very similar) is a core feature of phpBB: https://www.phpbb.com/support/docs/en/3.2/kb/article/how-to-configure-q%2Ba-captcha/ https://www.phpbb.com/support/docs/en/3.2/kb/article/how-to-... It works very well.