Unfortunately, there is no captcha that could provide 100% spam protection. Real people (and spammers) can get through captcha easily. Here is a list of simple recommendations to stop spam on your WordPress website:
- Make sure that the Captcha plugin is installed, activated, updated to the latest version and integrated with your form(-s).
- Enable all captcha protection complexity. Go to the plugin settings page and enable such options as Plus, Minus, Multiplication; enable Numbers, Images, and Words.
- Try to submit form(-s) with captcha (use the wrong answer to make sure that Captcha is working correctly).
- Install and activate Limit Attempts plugin to get additional anti-spam protection and low-down bots registration rate.