3.1. Designing and Testing Incident Response Plans

When a GuardDuty finding fires at 2 AM showing active credential exfiltration, your team has minutes — not hours — to contain the blast radius. Plans that exist only on paper will fail in this moment. The difference between organizations that recover quickly from breaches and those that don't is almost never technical capability — it's preparation. Imagine a fire department that had never practiced with their equipment: they have the truck, the hoses, the training manual — but when the alarm sounds, nobody knows which hose connects where. That's what happens when IR plans aren't tested. Without tested response plans, teams make critical errors under pressure — they terminate compromised instances (destroying forensic evidence), grant emergency access that's never revoked (creating new vulnerabilities), or escalate to the wrong team (wasting hours). What makes AWS IR planning unique? Cloud environments are API-driven, which means both attacks and responses can be automated — and the exam expects you to design automated response workflows.

This section covers how to design response plans and runbooks, prepare your environment for incidents, test IR plans effectively, and automate remediation.

Scenario: Your company passed a SOC 2 audit last quarter, but the IR plan was never actually tested. A real incident reveals that the runbook references services that were decommissioned 6 months ago and contacts team members who've left the company.

Reflection Question: Why does the exam emphasize IR plan testing as much as IR plan creation, and what specific AWS services enable realistic testing?