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DNS Investigations: Resolution, Telemetry, and Threat Decisions

Interpret resolution and DNS telemetry in context and support bounded threat decisions with this free investigation course.

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Experience level
Intermediate
Curriculum
3 modules · 6 lessons
Estimated reading
18 min
Language
English

Reading estimates use lesson text and an allowance for diagrams. Reflection, exercises and optional linked resources take additional time. These are estimates, not measured completion times.

KNOW WHAT YOU’RE WORKING TOWARD

What you’ll learn

  • Trace a DNS answer through client, recursive, cache, delegation, and authoritative roles.
  • Interpret common record types, TTLs, NXDOMAIN, NODATA, and resolution failures without inventing chronology.
  • Assess resolver and endpoint telemetry while accounting for identity, encrypted DNS, caching, and retention gaps.
  • Test suspicious-domain, tunneling, and beaconing hypotheses and produce precise response recommendations.

Is this the right course for you?

Who it’s for

Analysts who understand basic networks and want to investigate DNS evidence.

Scope and boundaries

DNS-focused evidence interpretation. A DNS observation alone does not establish who controlled a host or whether a connection succeeded.

How you’ll learn

Self-paced reading with explanatory diagrams and linked resources. Reflection and optional resource study take additional time.

Before you begin

  • Basic IP networking and log analysis — Learners should understand IP addresses, client-server communication, timestamps, and the purpose of logs. Prior DNS administration or packet-capture expertise is not required.

About this course

DNS data appears in phishing, malware, endpoint, cloud, and network investigations, yet it is easy to overread. This course gives SOC analysts, threat hunters, and network defenders a working model of stub resolvers, recursive resolvers, authoritative servers, resource records, TTLs, negative caching, encrypted transports, and enterprise logging. Learners examine suspicious domains and query patterns without treating lexical oddity, NXDOMAIN volume, or a reputation result as proof. They correlate client, resolver, DHCP, endpoint, proxy, and identity evidence; test tunneling and beaconing hypotheses; and document bounded conclusions. Completion means the learner can reconstruct what a DNS record proves, identify the client and collection boundary, scope related activity, and recommend precise blocking or follow-up with stated confidence.

FOLLOW THE LEARNING PATH

Course curriculum

MODULE 1

1. Understand What DNS Evidence Represents

Build the resolution and caching mental model required to interpret observations at the correct system and time.

  1. Trace the Resolution ChainFollow a query from an application through local and recursive caches to authoritative data, and identify what each observer can actually record.3 min reading
  2. Read Records, TTLs, and Negative AnswersInterpret common record sets and caching behavior so a current lookup is not mistaken for historical truth.3 min reading

MODULE 2

2. Collect and Evaluate Suspicious DNS Activity

Design a trustworthy evidence path, then evaluate domains and query patterns using context instead of brittle visual heuristics.

  1. Know Your Resolver Telemetry and Blind SpotsInventory managed resolvers, forwarders, endpoint sensors, encrypted DNS, retention, and identity joins before trusting a query history.3 min reading
  2. Assess Domains Without Turning Heuristics into VerdictsCombine name, registration, hosting, certificate, record, use, and organizational context while resisting visual and reputation shortcuts.3 min reading

MODULE 3

3. Test Threat Hypotheses and Respond

Analyze tunneling and periodic behavior with baselines, then pivot into a complete incident scope and proportionate DNS response.

  1. Test Tunneling and Beaconing HypothesesAnalyze query volume, labels, types, timing, responses, and client behavior while controlling for software that legitimately produces machine-generated DNS.3 min reading
  2. Pivot, Scope, Block, and ReportTurn one suspicious query into a time-bounded scope, choose a precise control, and record what the DNS evidence does and does not establish.3 min reading

Sources and editorial review

Reviewed by Threat Intelligence Lab

Sources linked in the lessons provide context and further reading. Check the original documentation for current platform behavior and requirements.

Selected references are shown here; the lessons contain the full reading lists.

About this learning content: Courses, lessons, assessments, explanations and illustrations may be created with the help of artificial intelligence. We review and check the material and do our best to avoid incorrect or outdated information, but mistakes, omissions or ambiguous questions may remain. Please verify information before relying on it for professional, security, legal or operational decisions. Read the full notice or report an issue.