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39. Malware Threats

39.5 Indicators of Compromise (IOC)

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IOC = clue that intrusion / malware happened or is happening.

Common classes:

  • File hashes (MD5/SHA1/SHA256) of known-bad binaries
  • C2 domains / IPs / URLs in DNS or proxy logs
  • Unusual processes – powershell -enc ..., Office spawning cmd.exe, random names in %Temp%
  • Autoruns – Registry Run keys, scheduled tasks, services, startup folders
  • DNS spikes – sudden queries to weird DGA-like names; beacon timing

Blue workflow: collect IOC → hunt in SIEM / EDR → isolate hosts → eradicate → lessons. IOCs expire fast (attacker re-packs) – behaviour detections jast durable.

# Linux lab VM – look at listening / established (concepts; your lab only)
ss -tulnp
# Amazon Linux style service check after you install audit tools you choose
sudo service auditd status
Red team (attacker) does Blue team (defender) detects / stops
Rotates domains / re-packs binaries (hash churn) Behaviour rules + threat intel feeds; focus on process ancestry
Installs persistence via Run key / task / service Autoruns baselines; Alert on new tasks under user profiles; Sysmon
Beacons every N minutes to C2 Proxy/DNS anomaly; JA3/TLS patterns where tooling allows; blocklist

Ravindra Bagale's Tip

Students block one hash and say "secure". A hash is yesterday's news. Process tree + network egress + persistence hunting = today's Blue work. CEH exam modules include IOC terminology – keep the definitions clear.

Practice task

Amir (fictional junior SOC, Pune) la 6 IOC milale: 2 hashes, 1 domain, 1 IP, 1 weird task name, 1 parent-child (WINWORD → powershell). Priority order liha: isolate host aadhi ki hash firewall block? 8-line runbook.

Real incident: NotPetya (2017)

NotPetya (reported by national CERTs and major outlets) looked like ransomware to many victims but behaved as a destructive wiper in important analyses – data recovery by paying was not a reliable path. Spread used credential theft and SMB lateral patterns after initial supply-chain style foothold (MeDoc update ecosystem – public reporting). Defence: segmentation, backup isolation, patch, identity hygiene. Source: CERT and major technical postmortems (verify).

Extended teaching notes

Why this lesson matters

Malware analysis in this course is defensive: recognise indicators, isolate hosts, preserve evidence. Never run unknown malware on your main OS or on someone else's network.

  1. Isolate the host from the network.
  2. Capture volatile data if trained to do so.
  3. Hash samples; search only in licensed/safe tools.
  4. Rebuild from a known-good image when unsure.
  5. Share IOCs with your SOC, not on random chats.

Mini case study

Suppose we are on a purple-team exercise for an Indian mid-size company (sample data). Red notes a technique from this lesson against a lab clone. Blue must show the control that stops it, the log that would have fired, and the ticket that hardens production. That is the standard this course trains you for.

Defender's worksheet (do this today)

  1. Write the lesson title, date and the exact lab target you are allowed to use.
  2. List three owned systems (VMs, apps, or cloud accounts) where this lesson applies.
  3. Run one safe check from the lesson on a lab system only. Paste the command and output.
  4. Write a two-sentence fix you would give a teammate.
  5. Name one related public advisory (CERT-In, CISA, NVD, or a vendor bulletin) with its date.

Indian workplace (sample data)

Suppose we are a junior analyst at Infosys, TCS, Wipro or a fintech SOC in Bengaluru/Pune. Turn this lesson into one checklist item with an owner, a due date and a place to store evidence (ticket + screenshot).

Global practice

Compare your notes with OWASP, CIS Benchmarks, NIST CSF/IR guidance or a cloud Well-Architected security question. Write five lines on what overlaps.

Everyday analogy

Explain the risk and the fix to a family member without jargon. If they can repeat the warning, you understand it well enough to teach juniors.

Key terms

  • Control: a safeguard (patch, config, process, detection).
  • Finding: a weakness backed by evidence.
  • Remediation: the fix plus how you verified it.
  • Scope: systems you have written permission to touch.
  • Least privilege: only the access the task needs.
  • Defence in depth: several layers so one failure does not end the story.

Common mistakes

  • Skipping written permission "just for a quick scan".
  • Practising on hostel, office or public targets without authorisation.
  • Collecting tool output without writing the fix.
  • Copying attack steps onto production to "verify". Defenders verify with versions, configs and patches.
  • Publishing screenshots that contain secrets, cookies or internal hostnames.

Recap

  • Evidence, fix, owner, date.
  • Own lab only.
  • Fix > spectacle.