The simplicity of it is logic defying. It used to be that you had to find crosswalks or move puzzle pieces or type blurred letters and numbers, but NOW all the sudden I can just click a box and HEY!, I’m human?
That’s hardly the Turing Test I’d expected.
Smarter bots know how to easily avoid being detected based on the speed of their requests by simply adding a random delay to them. A few years ago we discovered a very slow speed credential stuffing attack (testing usernames & passwords) against my employers site. It was only testing one set of credentials every couple of minutes.
Once we discovered it we didn’t block it though. We were able to spot the attack fairly easily once we knew what to look for, so we updated our system to always return a login failure no matter what credentials they sent.