The implementation of application whitelisting begins with creating a list of approved applications. In its simplest form, the application whitelisting program looks at the predefined file attributes associated with whitelisted applications, such as the file name, file path, and file size, to determine whether an application is allowed to run and, optionally, by which user. Attackers can quite easily replace whitelisted applications with malicious apps that have the same size and the same filename as a permitted application if the application whitelisting program is only using simple attributes to verify the program that is requesting to run. Therefore, it is advisable that the application whitelisting software you are going to implement is using cryptographic hashing techniques coupled with digital signatures linking executables and applications to their software developers as determining attributes of the application's identity and validity.