ICS Investigation playbook: Incident Response Plan

Preparation:

1. Develop and maintain an up-to-date inventory of ICS assets, including hardware, software, firmware, and network devices, along with their configurations, patch levels, and communication relationships.
2. Establish a baseline of normal ICS operations, including communication patterns, expected system behaviors, and performance metrics, to help identify deviations and potential security incidents.
3. Regularly review and update the ICS security policies and procedures, ensuring they are aligned with industry standards and frameworks, such as NIST SP 800-82 and IEC 62443.
4. Train the DFIR team in ICS-specific technologies, protocols, and vulnerabilities, and conduct regular tabletop exercises and simulations to evaluate their readiness and effectiveness.
5. Implement network segmentation, access controls, and monitoring solutions to isolate critical ICS components and detect potential security incidents early.

Detection and Analysis:

1. Continuously monitor network traffic for anomalies, focusing on ICS-specific protocols and using deep packet inspection (DPI) tools to analyze the content and detect potential malicious activities.
2. Review logs from ICS components and network devices for unusual or suspicious events, using Security Information and Event Management (SIEM) solutions to aggregate and correlate logs for better visibility and faster analysis.
3. Analyze user access and activity records to identify potential insider threats, unauthorized access, or misuse of system privileges, implementing User and Entity Behavior Analytics (UEBA) tools to detect deviations from normal behavior patterns.
4. Leverage threat intelligence sources, such as ISACs, vendor advisories, and open-source intelligence (OSINT), to stay informed about known threats, vulnerabilities, and attack techniques targeting ICS environments.
5. Establish alert thresholds and triggers for potential security incidents based on the baseline of normal operations, implementing automated response capabilities where possible to minimize the impact of incidents.

Containment and Eradication:

1. If an incident is detected, initiate containment measures to prevent further damage or unauthorized access, such as isolating affected systems, revoking user credentials, or blocking suspicious network traffic.
2. Gather relevant artifacts, such as forensic images, memory dumps, and malware samples, using chain-of-custody procedures to maintain the integrity of the evidence for potential legal actions.
3. Perform in-depth analysis of firmware, software, and configuration files to identify vulnerabilities, backdoors, or other security flaws, using reverse engineering tools and static/dynamic code analysis techniques.
4. Inspect physical devices for signs of tampering, unauthorized connections, or modifications, collaborating with facility management and physical security teams to ensure a comprehensive assessment.
5. Review historical data and trends to identify patterns that may indicate potential security issues or areas of concern, leveraging data analytics and machine learning techniques to improve detection capabilities.

Remediation and Recovery:

1. Implement necessary patches, updates, and configuration changes to address identified vulnerabilities and security gaps, ensuring proper testing and validation before deployment.
2. Remove any detected malicious software, unauthorized users, or unauthorized modifications to ICS components, following best practices for malware removal and system hardening.
3. Restore affected systems to their pre-incident state using backups, redundant systems, or vendor-provided recovery tools, ensuring that restoration processes do not reintroduce vulnerabilities or malicious elements.
4. Validate the integrity and functionality of the restored systems through extensive testing, including functional tests, performance tests, and security assessments.
5. Gradually reintegrate the affected systems back into the ICS environment, closely monitoring for any signs of recurring issues or new security incidents.

Lessons Learned and Improvement:

1. Conduct a post-incident review to analyze the DFIR process's effectiveness and identify improvement areas.
2. Update the ICS inventory, baseline, and security policies based on the lessons learned from the investigation.
3. Implement additional security measures, such as network segmentation, strong authentication, and employee training, to strengthen the ICS security posture.
4. Share relevant information and findings with industry peers and ISACs to help improve collective security awareness and defenses.