1. What is DNS?

• DNS = Domain Name System
• Think of it as the phonebook of the internet.
• It translates human-readable domains (example.com) into IP addresses (93.184.216.34) that computers use.

2. How DNS Works (Step by Step)

When you type www.example.com:

1. Browser/OS cache → Checks if it already knows the IP.
2. DNS Resolver (usually your ISP or 8.8.8.8) → Starts the query.
3. Root DNS Server → Says: “I don’t know, but .com servers do.”
4. TLD Server (.com) → Says: “Ask the authoritative server for example.com.”
5. Authoritative DNS Server → Responds with the final IP address.
6. Browser connects to that IP.

3. DNS Record Types (Important for Pentesting)

• A record → Maps domain to IPv4 (e.g., example.com → 93.184.216.34).
• AAAA record → Maps domain to IPv6.
• CNAME → Alias for another domain (useful for subdomain takeovers).
• MX record → Mail servers for the domain.
• TXT record → Arbitrary text (often used for SPF, DKIM, DMARC).