Secure attention key explained

A secure attention key (SAK) or secure attention sequence (SAS)^[1] 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.

Examples

Some examples are:

• for Windows NT.^{[1] [2]}
• default sequence for Linux.^[3] Not a true C2-compliant SAK.^[4]
• for PLATO IV in the 1970s.^[5]

See also

• Control-Alt-Delete
• Magic SysRq key
• Break key

Notes and References

1. Web site: S (Security Glossary) - Win32 apps Microsoft Learn. Microsoft. 2023-04-02.
2. Web site: Secure Attention Sequence (SAS) - Network Encyclopedia. 2023-04-02.
3. Web site: Linux 2.4.2 Secure Attention Key (SAK) handling. Andrew Morton. Andrew Morton (computer programmer). 2001-03-18. Linux Kernel Organization. 2011-05-30.
4. Web site: Linux Magic System Request Key Hacks. 2013-08-12. kernel.org. 2017-05-21.
5. Web site: PLATO User's Guide. Control Data Corporation. 1981-04-30. 2023-04-21.