Ravindra BagaleCourses & study guides

31. SOC, SIEM and Incident Response

31.5 Alert Triage

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In short: Triage means quickly deciding what each alert is and what to do next.

Triage means quickly deciding what each alert is and what to do next.

Outcome Meaning Example
True positive Real attack, alert is correct Brute force followed by successful login from an unknown foreign IP
False positive Alert fired but nothing bad happened Admin mistyped their password five times
True negative No alert, nothing bad Normal traffic
False negative Attack happened but no alert – the most dangerous Attacker used a valid stolen password during office hours

An L1 triage routine for every alert:

  1. Read the alert: what rule, which host, which user, which source IP, what time.
  2. Enrich: is the IP internal or external? Check reputation on services like AbuseIPDB or VirusTotal. Is the user real and expected on this host?
  3. Scope: did the same IP or user touch other hosts? Any success after the failures?
  4. Decide: false positive (close with a note), or true positive (escalate to L2 with evidence).
  5. Document everything in the ticket: what you checked, what you found, why you decided.

Severity usually considers impact (production server, customer data) and confidence. A failed scan against a patched web server is low; an admin login from a new country followed by a new user being created is critical.

Ravindra Bagale's Tip

Writing only "false positive – closed" in a ticket is the most common L1 mistake. Write why it is a false positive: "User Sneha entered the wrong password 5 times over VPN, then logged in with the correct password; the IP belongs to the company." This is very useful for the next shift and for audits.

Practice task

For each alert, decide true or false positive and write a one-line ticket note: (1) 40 failed SSH logins from an external IP, no success; (2) 5 failed logins then success for user admin from a new country at 3 a.m.; (3) Nikto scan alert from the company's own vulnerability scanner IP during an approved scan window.