What is defined as a set of file hashes, certificates, or other custom rules crucial for the functioning of an application?

The correct answer, defined as a set of file hashes, certificates, or other custom rules crucial for the functioning of an application, aligns with the concept of an Application Definition.

Application Definition encompasses the specific attributes that identify and validate an application within security frameworks. These attributes include the file hashes, which serve as unique signatures for files, and certificates that authenticate the legitimacy of applications. By establishing these custom rules, organizations can dictate which applications are allowed to run, thus enhancing security and preventing unauthorized software from executing within their environments.

This definition is fundamental in application whitelisting and serves as a cornerstone in proactive security measures, ensuring that only verified applications are permitted to operate.