DNS stands for “Domain Name System”. The purpose of DNS is convert a domain name, such as “analogbit.com” to an ip address, such as “126.96.36.199”. The interesting thing about DNS queries is that they are usually recursive queries. This means that if a server doesn’t know the answer for a domain name, it is allowed to ask other servers for the answer. So while a firewall or restrictive ISP may filter regular internet traffic they probably overlooked DNS traffic.