Help with Banning Malicious Proxy Users?

[evolution2]

I am having a problem with banned users accessing my forum via proxies. I would like to prevent this but do NOT want to block people who may be using proxies to access the forum for legitimate purposes from a university or corporation. I’m not very technical, but is this at all possible or is there anything I can do to help my situation? I don’t know but suspect that proxies used by universities and corporations are somehow different than ones designed for anonymity and there would be a way to distinguish between the two in a most situations. I am using version 4.1.10. Thanks so much!