User Account Control (UAC) is a technology and security infrastructure introduced with
Microsoft's
Windows Vista operating system. It aims to improve the security of
Microsoft Windows by limiting
application software to standard user privileges until an
administrator authorizes an increase in privilege level. In this way, only applications that the user trusts receive higher privileges, and
malware should be kept from receiving the privileges necessary to compromise the operating system. In other words, a user account may have administrator privileges assigned to it, but applications that the user runs do not also have those privileges unless they are approved beforehand or the user explicitly authorizes it to have higher privileges.
Tasks that require administrator privileges will trigger a UAC prompt (if UAC is enabled) are typically marked by a 4-color security shield symbol. In the case of executable files, the icon will have a security shield overlay. Ed Bott's
Windows Vista Inside Out lists the following tasks which require administrator privileges:
- Changes to system-wide settings or to files in %SystemRoot% or %ProgramFiles%
- Installing and uninstalling applications
- Installing device drivers
- Installing ActiveX controls
- Changing settings for Windows Firewall
- Changing UAC settings
- Configuring Windows Update
- Adding or removing user accounts
- Changing a user’s account type
- Configuring Parental Controls
- Running Task Scheduler
- Restoring backed-up system files
- Viewing or changing another user’s folders and files
Common tasks, such as changing the time zone, do not require administrator privileges (although changing the system time itself does, since the system time is commonly used in security protocols). A number of tasks that required administrator privileges in earlier versions of Windows, such as installing critical Windows updates, no longer do so in Vista. Any program can be run as administrator by right-clicking its icon and clicking "Run as administrator".