BOPM uses a technique known as "DNS blacklists" basically, it adds blacklisted hosts (in this case proxies) to a DNS zonefile. When you try and connect to a server, if BOPM is running, it will then query this DNS record, and if it is found, it means you get banned because you are using a proxy. If it is not found, it will then resort to scanning you completely, meaning connecting to you on common ports to determine if you run a proxy. If you do, it will then send a report back to the BOPM people telling them you found a new proxy, they will verify this, and if it is true, they will add it to the DNS blacklist.
