DNS Investigations: Resolution, Telemetry, and Threat Decisions
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.
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.
Before you begin
You will get more from this course if these foundations are already familiar.
- 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.
Course content
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.
Trace the Resolution Chain
Follow a query from an application through local and recursive caches to authoritative data, and identify what each observer can actually record.
Read Records, TTLs, and Negative Answers
Interpret common record sets and caching behavior so a current lookup is not mistaken for historical truth.
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.
Know Your Resolver Telemetry and Blind Spots
Inventory managed resolvers, forwarders, endpoint sensors, encrypted DNS, retention, and identity joins before trusting a query history.
Assess Domains Without Turning Heuristics into Verdicts
Combine name, registration, hosting, certificate, record, use, and organizational context while resisting visual and reputation shortcuts.
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.
Test Tunneling and Beaconing Hypotheses
Analyze query volume, labels, types, timing, responses, and client behavior while controlling for software that legitimately produces machine-generated DNS.
Pivot, Scope, Block, and Report
Turn one suspicious query into a time-bounded scope, choose a precise control, and record what the DNS evidence does and does not establish.