Incident Response & Digital Forensics
When prevention fails, incident response determines how much damage occurs. Digital forensics provides the evidence to understand what happened and how to prevent recurrence. The difference between a minor incident and a catastrophic breach often lies in response speed.
Incident Response Lifecycle
The NIST SP 800-61 four-phase model (Preparation, Detection & Analysis, Containment & Eradication, Post-Incident Activity) guides effective incident handling.
Preparation
Building capabilities before incidents occur: policies, tools, training, and communication plans.
Identification
Detecting and determining whether an incident has occurred, its scope and impact.
Containment
Limiting damage by isolating affected systems while preserving evidence.
Eradication
Removing threat elements and vulnerabilities from systems.
Recovery
Restoring systems to normal operation and verifying integrity.
Lessons Learned
Reviewing incident response effectiveness and updating procedures.
Digital Forensics Artifacts
Digital forensics examines multiple artifact types to reconstruct attack timelines and identify attacker methods. Proper collection preserves evidence integrity for legal proceedings.
File System
Deleted files, timestamps, file access patterns, hidden data.
Autopsy, EnCase, FTK, sleuthkit
Timeline reconstruction, deleted malicious files, data exfiltration evidence.
Registry (Windows)
System configuration, installed software, user activity, persistence mechanisms.
RegRipper, RECmd, Registry Explorer
Startup entries, malware persistence, user activity reconstruction.
Event Logs
System events, login attempts, process creation, service changes.
EventLog Explorer, LogParser, Splunk
Account compromises, lateral movement, malicious activity timeline.
Network Traffic
Connections, DNS queries, protocol anomalies, data exfiltration.
Wireshark, Zeek, NetworkMiner
C2 communication, data theft, attack vector identification.
Memory
Running processes, network connections, injected code, encryption keys.
Volatility, Rekall, DumpIt
Fileless malware, process hollowing, in-memory payloads.
Chain of Custody
Legal admissibility of digital evidence requires maintaining an unbroken chain of custody. Any break can render evidence inadmissible in court proceedings.
Incident Severity Classification
Not all incidents require the same level of response. Proper classification ensures appropriate resources are allocated efficiently while maintaining stakeholder communication.
Level 1 - Low
Examples: False positives, policy violations, minor anomalies
Response: Document and monitor
Level 2 - Medium
Examples: Malware infection, unauthorized access attempts
Response: Contain and investigate
Level 3 - High
Examples: Data breach, system compromise, ransomware
Response: Activate IR team, executive notification
Level 4 - Critical
Examples: Nation-state attack, critical infrastructure impact
Response: Legal notification, law enforcement, regulatory bodies
Key Takeaways
- IR is a process—preparation and lessons learned are as critical as active response.
- Forensics artifacts tell the story of an attack—collect and preserve them properly.
- Chain of custody ensures evidence admissibility in legal proceedings.
- Severity classification enables appropriate response scaling and resource allocation.