53 - Pentesting dns
DNS stands for "Domain Name System". It is a decentralized system for mapping domain names (such as www.example.com) to IP addresses (such as 192.0.2.1). The DNS is like a phone book for the internet, translating human-friendly domain names into the numerical addresses that computers use to communicate with each other. When you type a domain name into your web browser, your computer sends a request to a DNS server, which looks up the corresponding IP address and returns it, allowing your computer to establish a connection to the desired website.
nmap
ISC BIND
dig 53
dig @$IP chaos version.bind txt
dig @$IP chaos hostname.bind txt
dig @$IP chaos authors.bind txt
dig @$IP chaos ID.server txt
dig - zone transfer