Application integrity is the security goal of ensuring that only approved, unmodified software can run on a system. It goes beyond detecting malware after launch: it checks that an application has not been replaced, patched, injected into, or tampered with before execution. Controls such as code signing, hash verification, secure boot, and application allowlisting help enforce it.
This matters because many attacks rely on changing what a host runs. Adversaries may drop a malicious executable, modify a trusted binary, or use unauthorized scripts and loaders to gain persistence. In defense, application integrity reduces that risk by blocking unknown or altered code, especially on sensitive endpoints and OT systems where downtime and validation are costly. In practice, it supports zero-trust operations by treating software trust as something that must be verified continuously, not assumed.