Secure attention key
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A secure attention key (SAK) or secure attention sequence (SAS) is a special key or key combination to be pressed on a computer keyboard before a login screen which must, to the user, be completely trustworthy. The operating system kernel, which interacts directly with the hardware, is able to detect whether the secure attention key has been pressed. When this event is detected, the kernel starts the trusted login processing.
The secure attention key is designed to make login spoofing impossible, as the kernel will suspend any program, including those masquerading as the computer's login process, before starting a trustable login operation.
On systems that are configured to use a SAK, users must always be suspicious of login prompts that are displayed without having pressed this key combination.
In Microsoft Windows this is handled by the Winlogon component. Use of a secure attention key can also be required by the Windows User Account Control (UAC) prompt.
Examples
Some examples are:
- Ctrl+Alt+Del for Windows NT-based systems (called Secure Attention Sequence)
- Alt+SysRq+K default sequence for Linux[1]
- Ctrl+X Ctrl+R for AIX
- Break for OpenVMS
- ⇧ Shift+Stop for PLATO IV in the 1970s.
Use by BIOS
A similar combination, such as Ctrl+Alt+Del, is often used by a PC system BIOS to force a reboot during a boot sequence.
See also
References
- ^ Andrew Morton (2001-03-18). "Linux 2.4.2 Secure Attention Key (SAK) handling". Linux Kernel Organization. Retrieved 2011-05-30.
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