File integrity in IT refers to the process of protecting a file from unauthorized changes, including cyber-attacks. In other words, a file’s 'integrity’ is validated to determine whether or not it has been altered after its creation, curation, archiving or other qualifying event.
Techopedia explains File Integrity
Tech companies have built various file integrity monitoring tools to help system administrators determine whether a file’s integrity is intact. IT pros who perform file integrity monitoring sometimes use the "checksum" method to compare two versions of a data set.
In addition, many file integrity monitoring tools use "hashing," a method of creating and comparing cryptographic keys to determine whether a file has been altered or whether it has integrity. Some of these tools feature new automated "agent-less" monitoring, which was developed to cut costs; these tools perform a more thorough job of integrity monitoring and require less work in terms of deployment and implementation.