Proxy.
Attempts to block evil users like spam bots.
Does things like analysing suspicious IPs. One source is https://en.wikipedia.org/wiki/Project_Honey_Pot
Makes users pass CAPTCHAs if they are found too suspicious.
Thread levels: https://support.cloudflare.com/hc/en-us/articles/200170116-What-do-the-Threat-Scores-mean-
https://support.cloudflare.com/hc/en-us/articles/204191238-What-are-the-types-of-Threats-
I'm under attack PhantomJS override: https://www.snip2code.com/Snippet/303823/This-is-a-project-designed-to-get-around