What is File Integrity Monitoring (FIM)?
A file integrity monitoring security program implements a detective control that compares selected system objects with a trusted baseline and reports change. Coverage may include files, directories, binaries, configurations, permissions, ownership, and related metadata. Tools commonly use cryptographic Hashing plus metadata comparisons, collecting events continuously or scanning on a schedule through agents or agentless access. The baseline, rules, credentials, and telemetry pipeline require protection because an attacker who alters them can conceal activity. NIST control SI-7 addresses integrity checks, unauthorized-change detection, and defined responses for software, firmware, and information. FIM establishes that something changed; without context, it cannot determine whether every change was malicious, erroneous, or an approved administrative action.
What is File Integrity Monitoring (FIM) used for?
FIM helps detect tampering, malware persistence, unauthorized configuration changes, and unexpected modifications to critical application or operating-system components. It also supports change-control validation, Incident Response (IR), forensic timelines, and compliance evidence. Effective programs prioritize high-risk scope, correlate alerts with approved deployments or package activity, tune exclusions carefully, preserve telemetry, and assign investigation ownership. Security Information and Event Management (SIEM) enrichment can combine change events with identity, process, endpoint, and network context to improve triage. Blind spots arise when agents are disabled, baselines remain mutable on monitored hosts, coverage is incomplete, or alert floods normalize high-risk changes. Assurance therefore depends on protected collection, health monitoring, severity rules, retention, and timely response—not merely deploying an agent.
