Linux Hardening in Hostile Networks: Server Security from TLS to Tor

7. DNS

Domain Name System (DNS) is one of those fundamental network services that many people never give a second thought (as long as it’s working). Yet most things that happen on a network, and even more so on the Internet, rely on DNS. At its most basic level, DNS converts a server’s name (like www.example.com) into its IP address (93.184.216.34) so that an end user doesn’t have to memorize the IP addresses for each the websites she wants to visit—she just types a hostname as part of a URL and gets to the site. Most servers inside a data center rely on DNS instead of IP addresses as well. After all, server IP addresses change—especially in the cloud—and it’s a pain to have to change every host in your network when an IP address changes. Instead, ...