This is CaptchaBot

With more than 500.000+ users automatically scanned and 60.000+ bad actors found, you can be sure that your server is safe from any kind of automated attack thanks to our constantly evolving Machine Learning algorithms. Our Machine-Learning Algorithm uses continuous learning, which means it's getting better without manual intervention.
Our network returns a confidence score, which allows you to customize how secure you want your server to be by posting extra security challenges if the confidence score is below a certain level. To customize your security level, visit the CaptchaBot Console.

To prevent bad actors and automated accounts from joining your server, we've developed a public reports database that keeps track of every bad actor that CaptchaBot came across. The Database is and will remain public for everyone. To visit the CaptchaBot Database, click here. If you are a developer looking to contribute to our Database or use our database for your Bot, view our APIs!

With the launch of URLGuard, our community-based URL rating system, we are also protecting your server from members posting ToS-breaking URLs that were reported to the CaptchaBot Team. To report and check a URL, click here!