"With the introduction of Windows Vista, Microsoft has added a new form of mandatory access control to the core operating system. Internally known as 'integrity levels', this new addition to the security manager allows security controls to be placed on a per-process basis. This is different from the traditional model of per-user security controls used in all prior versions of Windows NT. In this manner, integrity levels are essentially a bolt-on to the existing Windows NT security architecture. While the idea is theoretically sound, there does exist a great possibility for implementation errors with respect to how integrity levels work in practice. Integrity levels are the core of Internet Explorer Protected Mode, a new 'low-rights' mode where Internet Explorer runs without permission to modify most files or registry keys. This places both Internet Explorer and integrity levels as a whole at the forefront of the computer security battle with respect to Windows Vista."