It's not just the IP that is used
I'm well aware of that.......... was just keeping it simple!
Operating system name, Browser name, Browser Version, Screen Size, etc.
Plus the "
Almighty Cookie"
Screen size could be interrogated sometimes to determine if a proxy is being used
because some proxies were reserving some bytes and then the screen size became a non-standard size.
I was told that "TOR" proxies could not be detected, yet I was able to code a proxy detector for playing that was able to detect "TOR" proxies. I had one of your infamous sock puppets test it and it detected each proxy he tried on a private web site. That was a few years ago, have not played with it since, things probably have changed by now.
For those that do downloads and are restricted by being allowed only 1 download in a certain time limit, just delete the cookie and change your IP and you are good to go for another Download.