Secure attention key
A secure attention key (SAK), special attention key,<ref>Template:Cite web</ref> or secure attention sequence (SAS)<ref name=ms-sas>Template:Cite web</ref> is a special key, key combination or sequence 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, or init system is able to detect whether the secure attention key has been pressed. When this event is detected, the trusted login processing is started.
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:
- Template:Key press: Introduced in systemd v257 as a more reliable SAK for Linux distributions but may require support from the currently running desktop environment.<ref>Template:Cite web</ref> It is implemented as of gdm (GNOME display manager) 47.<ref>Template:Cite web</ref>
- Template:Key press on X Window System immediately kills the X server (although the key combination can be disabled<ref>Template:Cite web</ref>) and can be used to quickly and easily get back to the login prompt.<ref>Template:Cite web</ref>
- [[Magic SysRq key|Template:Key press]] default sequence for Linux.<ref name="Morton2001">Template:Cite web</ref> Not a true C2-compliant SAK.<ref name=":0">Template:Cite web</ref>
- Template:Key press then Template:Key press on AIX,<ref>Template:Cite web</ref> but it can be disabled.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>
- Template:Key press for PLATO IV in the 1970s.<ref>Template:Cite web</ref>
- [[Control-Alt-Delete#Windows NT family|Template:Keypress]] for Windows NT.<ref name=ms-sas/><ref>Template:Cite web</ref>