DNS, HTTP & the Web Stack

DNS translates names to addresses. A resolver walks the hierarchy: root → TLD → authoritative server. Record types: A (IPv4), AAAA (IPv6), CNAME (alias), MX (mail), TXT (SPF/DKIM), NS (delegation).

DNS is a favourite attacker channel: cache poisoning, subdomain takeover, and DNS tunnelling for exfiltration. Defenders watch for abnormally long TXT queries and high-entropy subdomains.

HTTP is request/response and stateless. A request has a method (GET, POST, PUT, DELETE), a path, headers and an optional body. Status codes: 2xx success, 3xx redirect, 4xx client error, 5xx server error.

State is bolted on with cookies and tokens. Nearly every web attack — session hijacking, CSRF, XSS, IDOR — exploits how state is managed.