This model reduces the ability for the browser, or anything included in the browser such
as an ActiveX control, to write, change, or delete information on the computer.
Protected Mode is available only on Windows Vista since it relies on new security
features in the operating system. These features include User Account Control (UAC),
Mandatory Integrity Controls (MIC), and User Interface Privilege Isolation (UIPI). UAC
allows programs to be run without administrator privileges, an issue that has plagued
many Microsoft products in the past. Since non-administrators do not have full rights to
the operating system, an application running with UAC has to overcome a lot more
hurdles to perform dangerous actions such as install malicious services on the base
system. Mandatory Integrity Controls allow Protected Mode IE to read but not make any
changes to all but a small number of system objects specifically labeled for such access
(specific files and registry keys). Lastly, UIPI restrictions prevent lower rights processes
from sending communication to higher rights processes, strengthening the security
barrier between them. Under UIPI, like MIC, other windows must specifically opt-in to
receiving only the messages they want from a lower rights process.
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