Complete Incident Response Guide

1. Incident Response Overview

Incident response (IR) is the organized approach to addressing and managing security incidents. A well-prepared IR capability minimizes damage, reduces recovery time and costs, and provides evidence for legal proceedings if necessary.

The NIST Incident Response Framework defines four phases: Preparation, Detection & Analysis, Containment/Eradication/Recovery, and Post-Incident Activity. Each phase builds on the previous and informs improvements for future incidents.

2. Preparation Phase

2.1 IR Team and Roles

2.2 IR Plan Components

• Incident classification and severity levels
• Escalation procedures and contact lists
• Communication templates and channels
• Playbooks for common incident types
• Evidence handling procedures
• External vendor and law enforcement contacts

2.3 Tools and Resources

# Essential IR Tools
- SIEM access and queries
- EDR/XDR console
- Forensic workstations
- Network capture tools (Wireshark)
- Log aggregation
- Documentation platform
- Secure communication channel

3. Detection & Analysis

3.1 Indicators of Compromise (IoCs)

• Unusual network traffic (volume, destinations, protocols)
• Failed login attempts, unusual authentication
• Unexpected system changes, new accounts
• Suspicious processes, scheduled tasks
• Security tool alerts (EDR, SIEM, IDS)
• External reports (vendors, law enforcement, users)

3.2 Initial Triage

# Key questions for initial triage:
1. What systems are affected?
2. What type of incident is this?
3. When did it start? Is it ongoing?
4. What is the potential impact?
5. Is sensitive data at risk?
6. How was the attack detected?

# Severity classification
P1/Critical: Active breach, data exfiltration ongoing
P2/High: Confirmed compromise, no active exfil
P3/Medium: Suspicious activity, unconfirmed
P4/Low: Policy violation, minor security issue

4. Containment

4.1 Short-Term Containment

Immediate actions to stop the spread and limit damage:

• Isolate affected systems (network segmentation, disable ports)
• Block malicious IPs/domains at firewall
• Disable compromised accounts
• Preserve volatile evidence before isolation

4.2 Long-Term Containment

# Long-term containment actions:
- Apply emergency patches
- Rotate compromised credentials
- Implement additional monitoring
- Deploy blocks across environment
- Set up honeypots/canaries to detect persistence

# Evidence preservation (before containment if possible):
- Memory dump
- Running processes
- Network connections
- Timestamp of actions

5. Eradication & Recovery

5.1 Eradication

• Remove malware and attacker persistence mechanisms
• Patch exploited vulnerabilities
• Reset all potentially compromised credentials
• Verify removal with security scans

5.2 Recovery

1. Restore systems from clean backups
2. Rebuild compromised systems (don't trust cleaning)
3. Implement hardening measures
4. Restore in stages with validation
5. Enhanced monitoring during recovery period

6. Post-Incident Analysis

6.1 Lessons Learned

# Post-incident review agenda:
1. Timeline of events
2. What worked well?
3. What could be improved?
4. Root cause analysis
5. Recommendations
6. Action items with owners and deadlines

6.2 Documentation

• Complete incident timeline
• Technical analysis report
• Indicators of compromise for sharing
• Cost and impact assessment
• Recommendations for prevention

7. Communication & Legal

7.1 Internal Communication

• Executive briefings at defined intervals
• Need-to-know basis during investigation
• Secure communication channels (not potentially compromised email)

7.2 External Communication

• Regulatory notification requirements (GDPR 72 hours, state breach laws)
• Customer notification if data affected
• Law enforcement engagement for serious crimes
• PR/media handling if public disclosure needed

8. Frequently Asked Questions

Conclusion

Effective incident response requires preparation before incidents occur. Build your team, develop playbooks, and practice regularly. During incidents, prioritize containment, preserve evidence, and maintain clear communication. Post-incident, learn and improve for next time—because there will be a next time.

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SIEM Guide Digital Forensics