Behavior blocking monitors file activities, preventing certain modifications to the operating system or related files. For example, behavior blockers may monitor the registry, and warn users accordingly if a file being executed is attempting to modify the system registry. Some files, of course, do this legimately, i.e. a SETUP program. Others, however, have malicious intent and try to modify the registry to launch on every startup or when a particular access is made.
Typically, behavior blocking software is permission-based, relying on the user to make the appropriate decision. While some find this method of behavior blocking intrusive, used properly it can be one of the best defenses against today's malware.

