Security Incident Response Plan Prompt

Help me draft a security incident response plan.

Organisation type: [e.g. 50-person SaaS company, healthcare provider, financial services firm]
Critical systems: [list your most important systems and data]
Current security tools: [list what you have]
Team: [who is responsible for security? Is there a dedicated team?]
Most likely threats: [e.g. phishing, ransomware, data breach, insider threat]

Please create:
1. Incident severity classification (P1–P4 with examples)
2. First-hour response checklist for a suspected breach
3. Communication plan (who to notify and when)
4. Containment and recovery steps for your top 2 threat scenarios
5. A post-incident review template