Microsoft App Control for Business can restrict which applications, binaries, scripts, and installers run on Windows. It is a policy-driven code integrity control. Audit mode is a useful way to discover what a policy would block, but the absence of blocks in audit mode is not proof that enforcement has been validated.
Microsoft's documentation says audit mode logs applications, binaries, and scripts that would have been blocked if the policy were enforced. It recommends starting in audit mode, using the events to refine the policy, and deleting the audit option to move to enforcement. Some capabilities can be active even in audit mode, especially when user mode code integrity is enabled. Supplemental policies inherit the base policy's mode.
That means two environments can both report that an App Control policy is present while having different effective behavior. A managed endpoint may have the base policy in audit mode, an enforced supplemental policy, or a policy that has not yet survived the restart required for enforcement. A configuration inventory should record the policy XML, its policy ID, the rule options, the deployment method, and the last reboot.
When moving from audit to enforce, build a test ring that exercises the applications users actually run. Include signed installers, line-of-business binaries, scripts launched by PowerShell, and software that loads unsigned plug-ins. An audit event can show that a binary ran, but it may not show whether the application completed its work after a dependent component was blocked. Test the workflow, not only process creation.
Useful checks include:
Confirm the policy is present in the effective policy set.
Verify the enforcement mode after the required restart.
Run an explicitly disallowed binary in a disposable test environment and confirm the block.
Run an approved binary from each important publisher and confirm success.
Review CodeIntegrity events for blocked files and policy load failures.
Compare the base and supplemental policy modes.
Policy scope matters. A file path rule can be unsafe if an ordinary user can write to that path. A publisher rule can be broader than the security team expects if the certificate signs many products. The documentation warns that some rule options and policy behaviors need careful testing, and that some changes are not reversible without deployment planning.
Audit mode should produce evidence, not confidence. The evidence includes which files would be denied, whether the applications still work under enforcement, and whether the policy state survives reboot and management updates. Keep a rollback policy and a test path for each change.
App Control is strongest when the team treats it as a controlled code integrity deployment. Enforcement readiness is a tested state, not a checkbox on a policy file.