Originally Posted by azguy

It's not easy to block proxy hits, but it is doable to some extent.

What you could theoretically do is, run a batch script that scans through your log of whatever type, extracts the IP address, and attempts to connect to it as if it was a proxy server (check all ports for an open HTTP/Socks proxy). This can be a slow process, which is why you should never do it on-the-fly and only in batch. Also, you shouldn't wait too long before you check an IP, as proxy servers tend to die fast and your `evidence` will be lost.

EDIT: Needless to say, when a proxy is found you can cancel that specific hit/sale or do whatever you want with your findings.