Module 21 · DNS Security — DoH, DoT, DNSSEC, Sinkholing

Manish Garg
Manish Garg Associate of (ISC)² · RingSafe
May 14, 2026
2 min read
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Why this module exists. DNS is the most-exploited and most-overlooked protocol layer. DoH, DoT, DNSSEC, and DNS sinkholing each address specific threats. This module covers the modern DNS security stack and operational patterns.

The classic DNS problems

  • Plaintext queries visible to network observers.
  • Response forgery / cache poisoning.
  • No cryptographic authenticity.
  • DNS used for data exfiltration.
  • DGA and fast-flux evading blocklists.
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