What "special devices" are you trying to block? That's the first thing you need to find out. Let me know here, and I will try giving you a code.
Yupp, I also believe fingerprint based ban would be the most suitable thing to do in OP's case.
I dunno how effective the following script is, but give it a try OP:
Code:
https://github.com/Valve/fingerprintjs2
Hopefully, that will solve your problem. They claim that the pro version of their script has accuracy of 99.5%. If true, that should be pretty good. I haven't tried them though.
