How do you plan to prevent abuse? E.g. this website allows someone to portscan another IP without exposing their own IP. Even with a per-IP throttle, someone with a botnet can use this website to effectively portscan any one host without exposing any of their botnet's IPs.<p>I've been using <a href="http://www.canyouseeme.org/" rel="nofollow">http://www.canyouseeme.org/</a> for this purpose. It does have the limitation that it only allows testing the ports of the connecting IP.