Postintrusion

Postintrusion is a term used in information security and risk management to describe the phase that follows the detection and containment of an intrusion. It encompasses the activities performed after an intrusion has been identified, with the goal of understanding impact, eradicating adversary access, restoring normal operations, and reducing the likelihood of recurrence. While the term is not universally standardized, it is commonly used in incident response frameworks to distinguish immediate containment from longer-term remediation and learning.

Key objectives include preserving evidence for forensics, accurately assessing data loss or exposure, removing backdoors and artifacts left by the attacker, applying security fixes and configuration changes, and restoring systems and services with integrity checks. The postintrusion phase also emphasizes governance tasks such as documentation, regulatory reporting where required, communication with stakeholders, and updating policies and training to prevent similar incidents.

Typical activities involve incident timeline reconstruction, root-cause analysis, threat-hunting to ensure no residual access remains, system hardening and patch management, backup validation and restoration, and changes-management oversight for legitimate reinstatement of services. A postintrusion review often culminates in a postmortem report and a lessons-learned session that informs future prevention and detection strategies.

Organizations may adapt postintrusion practices to cyber, physical security, or hybrid breaches, with roles distributed among incident response teams, security operations, legal/compliance, IT, and executive leadership. Challenges include maintaining evidence integrity, balancing rapid remediation with safe testing, and meeting regulatory requirements. Effective postintrusion processes aim to improve resilience by translating findings into concrete controls, training, and risk-aware governance.