TryHackMe DNS Room Lecture Notes

Introduction

• Presenter: John
• Topic: Understanding DNS (Domain Name System)
• Objective: Learn how DNS works to facilitate internet access.

Task 1: What is DNS?

• DNS Definition: Domain Name System.
• Purpose: Allows communication with devices on the internet without using IP addresses.
• IP Address Format: Four octets (e.g., 192.168.1.1).
• DNS Function: Maps domain names (e.g., tryhackme.com) to IP addresses.

Task 2: Domain Hierarchy

Top Level Domains (TLD)

• TLD Definition: Rightmost part of a domain name (e.g., .com, .org).
• Types of TLDs:
  • gTLD: Generic (e.g., .com, .org, .edu)
  • ccTLD: Country Code (e.g., .ca, .co.uk)
• New TLDs: Constantly emerging, e.g., .online, .club.

Second Level Domain

• Example: In "tryhackme.com", "tryhackme" is the second level domain.
• Restrictions:
  • 63 character limit
  • Characters allowed: A-Z, 0-9, hyphens (no starting/ending hyphens).

Subdomains

• Example: admin.tryhackme.com ("admin" is the subdomain).
• Restrictions:
  • Same as second-level domain
  • Maximum length: 63 characters
  • Unlimited creation

Task 3: DNS Record Types

Common DNS Records

• A Record: Resolves to IPv4 address.
• Pointer Records: For reverse lookups.
• Quad A Record: Resolves to IPv6 address.
• CNAME Record: Canonical name; maps domain to another domain.
• MX Record: Specifies mail exchange servers for domain.
• TXT Record: Stores text-based data (e.g., spam prevention, domain verification).

Task 4: Making a DNS Request

DNS Request Process

1. Local Cache: Checks recent lookups.
2. Recursive DNS Server: Usually ISP-provided; checks own cache.
3. Root DNS Servers: Redirect based on TLD.
4. TLD Servers: Directs to authoritative server.
5. Authoritative DNS Server: Provides final DNS record.

• TTL (Time to Live): Duration to cache response.

Task 5: Practical DNS Queries

• Using Website Queries: Practice DNS query commands.
• Example Queries:
  • CNAME for shop.website.thm
  • TXT record value for website.thm
  • MX record priority value
  • A record IP address for www.website.thm

Conclusion

• Resources: TryHackMe Discord and Subreddit for questions.
• Encouragement: Continue exploring DNS and happy hacking!