How to structure an Incident Response Plan (IRP) for ransomware defense and business continuity?

An Incident Response Plan for ransomware should combine a tiered containment workflow with predefined continuity checkpoints that are automated where possible. Align the plan to NIST CSF 4.0 and ISO 27001:2022 controls, and embed real‑time threat intel feeds.

Step‑by‑step framework

1. Preparation – Deploy Microsoft Defender for Endpoint (version 10.x) with AV, EDR, and Attack Surface Reduction rules (/C:"Set-MpPreference -AttackSurfaceReductionRules_Actions 0,1,1,1"). Sync MITRE ATT&CK v13 via ATT&CK Navigator.
2. Identification – Correlate alerts in SIEM (Splunk 9.x) using a SPL query:

index=endpoint sourcetype=defender status="blocked" | stats count by host, technique_id

Trigger if count > 5 within 10 min.
3. Containment – Execute network quarantine via Azure Network Security Group API:

$uri = "https://management.azure.com/subscriptions/$subId/resourceGroups/$rg/providers/Microsoft.Network/networkSecurityGroups/$nsgName?api-version=2023-09-01"
$body = @{properties=@{securityRules=@(@{name="Quarantine"; priority=100; direction="Inbound"; access="Deny"; sourceAddressPrefix="*"; destinationPortRange="*"})}} | ConvertTo-Json -Depth 5
Invoke-RestMethod -Method Put -Uri $uri -Body $body -Headers $authHeader

4. Eradication – Run Remove-Malware script on infected hosts, then verify with Get-MpThreatDetection until ThreatStatus = “Clean”.
5. Recovery – Restore from immutable snapshots (AWS EBS with --no-delete flag) and validate file hashes against known good baselines (sha256sum).
6. Post‑incident analysis – Populate IR ticket in ServiceNow (v8) with ATT&CK technique mapping, then run a root‑cause report (snc_ir_report.py).
7. Continuous improvement – Update playbooks in GitLab CI/CD, enforce a quarterly tabletop drill, and adjust thresholds in step 2 based on false‑positive rate.

Tool comparison

| Phase | Primary Tool | Automation |
|------------|------------------------|------------|
| Containment| Azure NSG API | Yes (REST) |
| Eradication| Defender PowerShell | Yes (script) |
| Recovery | AWS EBS immutable snap | Yes (CLI) |

Gotcha: Encrypted backups that lack air‑gap verification can become ransomware payloads; test restore from a cold‑storage vault before relying on them for RTO guarantees.