Blacklisting is an okay option, but as you said, it's tough to do so just going by your memory. In fact there are actually thousands of free, public domains, wh

Blacklisting is an okay option, but as you said, it's tough to do so just going by your memory. In fact there are actually thousands of free, public domains, which you will likely want to blacklist. Here's a good list (2013): https://gist.github.com/tbrianjones/5992856 https://gist.github.com/tbrianjones/5992856 P.S. Maybe someone should make an API to verify if a domain is free/public or not :)