CISA Shares Lessons Learned from an Incident Response Engagement

September 22, 2025 · CISA Cybersecurity Advisories · Severity: CRITICAL

Advisory at a Glance Executive Summary CISA began incident response efforts at a U.S. federal civilian executive branch (FCEB) agency following the detection of potential malicious activity identified through security alerts generated by the agency’s endpoint detection and response (EDR) tool. CISA identified three lessons learned from the engagement that illuminate how to effectively mitigate risk, prepare for, and respond to incidents: vulnerabilities were not promptly remediated, the agency did not test or exercise their incident response plan (IRP), and EDR alerts were not continuously reviewed. Key Actions Prevent compromise by prioritizing the patching of critical vulnerabilities in public-facing systems and known exploited vulnerabilities. Prepare for incidents by maintaining, practicing, and updating incident response plans. Prepare for incidents by implementing comprehensive and verbose logging and aggregate logs in a centralized out-of-band location. Indicators of Compromise  For a downloadable copy of indicators of compromise, see:  AA25-266A-JSON.stix_.json AA25-266A-STIX.stix_.xml Intended Audience Organizations: FCEB agencies and critical infrastructure organizations. Roles: Defensive Cybersecurity Analysts, Vulnerability Analysts, Security Systems Managers, Systems Security Analysts, and Cybersecurity Policy and Planning Professionals. Download the PDF version of this report AA25-266A advisory cisa shares lessons learned from ir engagement Introduction The Cybersecurity and Infrastructure Security Agency (CISA) is releasing this Cybersecurity Advisory to highlight lessons learned from an incident response engagement CISA conducted at a U.S. federal civilian executive branch (FCEB) agency. CISA is publicizing this advisory to reinforce the importance of prompt patching, as well as preparing for incidents by practicing incident response plans and by implementing logging and aggregating logs in a centralized...