&gt; they&#x27;d have to keep lists of IP addresses associated with the VPN services they want to block.<p>Yeah, that&#x27;s probably what they&#x27;re doing.  It wouldn&#x27;t be too hard for them to get the first 95% either - beyond ARIN&#x2F;NIC registration searches etc, they could just look for IP addresses that often have a large number of subscribers behind them, especially a large number of non-us subscribers.