Showing posts from August, 2017

Testing 36200 DNS servers

Introduction DNS is an important part of the Internet and the speed and security are paramount for a good browsing experience. I thought it would be a good idea to scan the internet for DNS servers and test every single one of them. However, the latency of a particular DNS server depends highly on the distance and connection technology between you and the DNS server, and since I'm geographically located in Denmark, the results speed-wise only pertain to people located in/around Denmark.
Testing methodology I scanned the IPv4 Internet using NMap on port 53/UDP and stopped the scan after a few hours. The results were DNS 36200 servers, some of which are owned by ISPs, companies and a whole lot of private people. Since the IP scan was randomized, it should represent a good sample.

Almost all DNS servers have some sort of caching mechanism that makes sure requested DNS names are kept for as long as the Time-To-Live (TTL) as defined by the domain owner. To ensure we don't just tes…