Windows 8 : Managing Internet Explorer - Understanding and configuring browser security settings (part 2) - Disabling Protected Mode

Understanding Protected Mode (non-enhanced)

To provide continuous protection while you’re using the web, Internet Explorer provides Protected Mode. Internet Explorer 10 includes a number of updates to Protected Mode.

In many organizations, employees continue to sign in to local computers using accounts that have far more privileges than are necessary to accomplish their work. Specifically, a great number of people have administrator access to their local desktop computers, although their rights are generally more restricted at the domain level. Because programs launched with the user’s sign-in have the same rights as the user account itself, this can create a significant attack vector by which malware can be introduced onto the computer.

This is when Protected Mode becomes useful. Rather than running under the context of the user’s full set of privileges, Internet Explorer operates with a very limited set of privileges. As a result, if someone browses to a website that attempts to deploy malicious code, the attack attempt would be limited to just a few areas of the system, none of them critical. Such malicious code would not have sufficient rights to perform software installations, access personal files, or perform other damaging operations.

Protected Mode operates based on the concept of integrity levels. Windows 8 is composed of securable objects, which include files, folders, and registry keys. Every securable object in Windows 8 has its own integrity level. The list of available integrity levels is shown in Table 1.

When Internet Explorer is running with Protected Mode enabled, it is operating at a low integrity level, limiting it to the low-integrity areas of the system. This prevents an errant Internet Explorer process from accessing sensitive areas of the system and restricts the damage it can do.

Windows 8 and Internet Explorer 10 introduce AppContainer, a new process-isolation mechanism that takes the Protected Mode feature found in earlier versions of Internet Explorer to the next level by blocking even more areas of the system from both read and write activities initiated by Internet Explorer, including a user’s personal files and certain network locations. All Windows 8 native apps use AppContainer to help protect the system.

Because Protected Mode restricts access to so many parts of the system, it follows that there would be significant compatibility issues with some websites, and users would face a multitude of user account control (UAC) elevation requests during which the operating system requests user permission to perform a potentially dangerous administrative function. However, this is not the case. When a user browses to a location that contains code requesting access to an area of the system protected by Protected Mode, by virtue of the Protected Mode Compatibility Layer the request is silently redirected to a safe, supported location.