I have come across lots of companies who are selling whois databases of all the active domains of most of the TLDs and ccTLDs. I was wondering from where do they get the data. I know all the registries provide zone file access to registrars. However, these companies are not even registrars. Moreover, the Verisign registry's zone data files contain only the domain names and the nameservers information as it is a thin registry. Also, even if you get access to the zone files and along with it the domain names list, you have to use tools like Watch My Domains to fetch the whois data. Again, there is a catch here. Some registrars like Godaddy don't allow access to the whois of the domains directly. You have to get the data from their websites. Even the connections to the port 43 is restricted. So, the question is how are they managing to retrieve the domains information.