Incident Response is the organised process through which an organisation prepares for, detects, analyses, contains, eradicates, recovers from, and learns from cybersecurity incidents. NIST's current SP 800-61 Rev. 3, published in April 2025, frames incident-response recommendations within broader cybersecurity risk management and the NIST Cybersecurity Framework 2.0. An incident is not necessarily synonymous with every security alert: an alert may represent suspicious activity requiring investigation, whereas an incident is an event or series of events that meets an organisation's defined threshold for security significance and response.
Preparation is a critical component because effective response depends on capabilities established before an incident occurs. Preparation can include incident-response policies, defined roles, escalation criteria, contact information, communication procedures, forensic capabilities, logging, monitoring, backups, endpoint controls, privileged-access arrangements, evidence-preservation procedures, legal and regulatory contacts, and relationships with external specialists. Response plans should identify who can authorise actions such as isolating systems, disabling accounts, blocking traffic, contacting customers, notifying regulators, or engaging law enforcement. Without predefined authority and procedures, technical teams can lose valuable time determining who is permitted to act during a rapidly developing event.
Detection and analysis transform raw security telemetry into an understanding of what is happening. Sources may include endpoint detection systems, network sensors, identity logs, application telemetry, cloud audit trails, email security systems, user reports, threat intelligence, vulnerability information, and alerts from external providers. Analysts establish timelines, identify affected assets and accounts, determine whether activity is malicious, estimate scope, and assess confidence. False positives are common, so incident classification requires contextual investigation rather than blindly treating every alert as an incident. Correlation across independent telemetry sources can reveal relationships that are invisible in isolated alerts.
Containment aims to prevent an incident from expanding while preserving the organisation's ability to investigate and recover. Short-term containment may involve isolating endpoints, blocking malicious infrastructure, disabling compromised accounts, restricting network paths, or suspending affected services. Longer-term containment may involve architectural changes, credential rotation, additional monitoring, or temporary controls while eradication is prepared. Actions must be selected carefully because indiscriminate isolation can destroy volatile evidence, disrupt critical business operations, alert an attacker prematurely, or remove access needed for investigation. Incident response is therefore a balance between speed, evidence preservation, operational continuity, and reduction of attacker capability.
Eradication removes the causes and mechanisms that allowed the incident to persist, while recovery restores trustworthy operation. Eradication can involve removing malware, eliminating persistence, correcting exploited vulnerabilities, resetting credentials, rebuilding systems, closing unauthorised access paths, and addressing misconfigurations. Recovery should verify that systems are clean, controls are functioning, monitoring is adequate, and restored services behave as expected. Simply restoring from backup does not guarantee recovery if the backup contains compromised software, stolen credentials remain valid, or the original vulnerability remains exploitable. Recovery therefore includes validation rather than merely returning systems to an earlier state.
Incident Response relies heavily on information sharing and coordination. NIST identifies cyber threat information as including indicators of compromise, adversary tactics, techniques and procedures, recommended detection or prevention actions, and findings from incident analysis. Relevant information can therefore move from an incident investigation into security monitoring, threat intelligence, vulnerability management, supplier risk management, and other organisations' defensive capabilities. Internally, incident information can also identify systemic control failures, such as inadequate logging, excessive privileges, weak segmentation, or insufficient employee reporting mechanisms.
Post-incident activity is more than writing a summary. A useful review identifies root and contributing causes, control failures, detection delays, response bottlenecks, decision points, affected assets, business consequences, and opportunities for improvement. Metrics can include time to detect, time to contain, time to eradicate, dwell time, number of affected assets, recurrence rates, and quality of evidence available to responders. These metrics need context because faster containment is not automatically better if it repeatedly destroys evidence or causes unacceptable operational disruption. Lessons should result in tracked corrective actions rather than remaining as undocumented observations.
Incident Response has inherent uncertainty because responders often work with incomplete information while an attacker may still be active. Organisations can also face simultaneous technical, legal, regulatory, financial, reputational, and operational consequences. Effective programmes therefore combine technical capabilities with governance, communication, business continuity, legal coordination, executive decision-making, and tested procedures. Current NIST guidance explicitly emphasises incorporating incident response throughout cybersecurity risk management rather than treating it as an isolated emergency function. Regular exercises, technical simulations, tabletop scenarios, log-review exercises, and controlled investigations help expose weaknesses before a real incident requires the organisation to rely on them.
