File integrity monitoring (FIM) is an internal control or process that performs the act of validating the integrity of operating system and application software files using a verification method between the current file state and a known, good baseline. This comparison method often involves calculating a known cryptographic checksum of the file's original baseline and comparing with the calculated checksum of the current state of the file.[1] Other file attributes can also be used to monitor integrity.[2]
Generally, the act of performing file integrity monitoring is automated using internal controls such as an application or process. Such monitoring can be performed randomly, at a defined polling interval, or in real-time.