Imported from jeremylongshore/tons-of-skills-marketplace (
skills/.curated/responding-to-security-incidents/SKILL.md). Install upstream withnpx skills add jeremylongshore/tons-of-skills-marketplace --skill responding-to-security-incidents. Copyright stays with the author (MIT).
Responding To Security Incidents
Overview
Guide the full NIST SP 800-61 incident response lifecycle: detection, containment, eradication, recovery, and post-incident analysis. Classify incidents by type (ransomware, data breach, DDoS, credential compromise, insider threat) and severity, then coordinate evidence preservation, threat containment, and root-cause investigation.
Prerequisites
- System and application logs accessible in
${CLAUDE_SKILL_DIR}/logs/(auth logs, web server logs, database access logs) - Network traffic captures (PCAP) or SIEM alert exports available
- Incident response team contact information and escalation paths documented
- Backup systems operational and recovery procedures tested
- Write permissions for incident documentation in
${CLAUDE_SKILL_DIR}/incidents/ - Forensic tools available: Volatility (memory), Autopsy/FTK Imager (disk), tcpdump/Wireshark (network)
Instructions
- Classify the incident: determine type (ransomware, data breach, DDoS, phishing, insider threat), assign severity (Critical/High/Medium/Low), and record initial detection timestamp and method.
- Scope affected systems: identify all compromised hosts, user accounts, data stores, and network segments. Map the blast radius.
- Preserve evidence before any changes: capture memory dumps (
volatility -f memdump.raw imageinfo), create disk images, export running process lists (ps auxf), and snapshot network connection state (ss -tulnp). - Collect log evidence: gather authentication logs (successful and failed), application error logs, firewall/IDS alerts, DNS query logs, and proxy server logs. Store originals in
${CLAUDE_SKILL_DIR}/incidents/evidence/. - Contain the threat: isolate affected systems from the network, disable compromised accounts, block malicious IPs at the firewall, and revoke compromised API keys or tokens.
- Investigate and reconstruct timeline: identify initial access vector, map lateral movement, determine data exfiltration scope, locate persistence mechanisms (cron jobs, startup scripts, web shells), and document all IOCs (IPs, hashes, domains, file paths).
- Eradicate the threat: remove malware and backdoors, patch exploited vulnerabilities, reset all potentially compromised credentials, and update firewall rules.
- Recover operations: restore from verified clean backups, rebuild compromised systems from hardened images, validate system integrity, and monitor for reinfection with heightened alerting.
- Document the incident: produce a comprehensive report at
${CLAUDE_SKILL_DIR}/incidents/incident-YYYYMMDD-HHMM.mdcontaining executive summary, detailed timeline, root cause analysis, IOC list, and lessons learned. - Create remediation backlog: list all follow-up actions (patch gaps, monitoring improvements, policy changes) with owners and deadlines.
See ${CLAUDE_SKILL_DIR}/references/implementation.md for the seven-phase implementation workflow.
Output
- Incident Report:
${CLAUDE_SKILL_DIR}/incidents/incident-YYYYMMDD-HHMM.mdwith timeline, root cause, IOCs, and impact assessment - IOC List: machine-readable indicators (IP addresses, file hashes, domains, YARA rules)
- After-Action Review: lessons learned, process gaps, and recommended improvements
- Remediation Backlog: prioritized follow-up tasks with owners and deadlines
Error Handling
| Error | Cause | Solution |
|---|---|---|
Critical logs missing from ${CLAUDE_SKILL_DIR}/logs/ |
Log rotation, deletion, or attacker tampering | Work with available data; note gaps; improve logging retention for future incidents |
| System state modified before evidence collection | First responder made changes before forensic capture | Document contamination; collect remaining evidence; prioritize network and SIEM logs |
| Attacker still has active access during investigation | Ongoing compromise detected | Prioritize containment over investigation; implement emergency network isolation |
| Permission denied accessing system memory | Insufficient forensic tool privileges | Escalate to obtain root/admin access; fall back to available log and network data |
| Backups encrypted or corrupted by ransomware | Attacker targeted backup infrastructure | Identify offline/air-gapped backups; assess rebuild-from-scratch feasibility |
Examples
- "Credential stuffing detected. Use logs in
${CLAUDE_SKILL_DIR}/logs/to triage the incident, scope affected accounts, and propose containment steps." - "Create an incident response plan for a suspected data breach: list evidence to collect, containment actions, and notification requirements."
- "Investigate a web shell found at
/var/www/html/uploads/cmd.php. Trace the initial access vector, identify persistence mechanisms, and produce an IOC list."
Resources
- NIST SP 800-61r2 Computer Security Incident Handling Guide: https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-61r2.pdf
- SANS Incident Handler's Handbook: https://www.sans.org/white-papers/33901/
- CISA Incident Response Guide:
- Volatility Framework (memory forensics): https://www.volatilityfoundation.org/
- Autopsy (disk forensics): https://www.autopsy.com/
${CLAUDE_SKILL_DIR}/references/errors.md-- full error handling reference${CLAUDE_SKILL_DIR}/references/examples.md-- additional usage examples- https://intentsolutions.io