A secure attention key (SAK), special attention key,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> or secure attention sequence (SAS)<ref name=ms-sas>{{#invoke:citation/CS1|citation |CitationClass=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.
ExamplesEdit
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>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref> It is implemented as of gdm (GNOME display manager) 47.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
- Template:Key press on X Window System immediately kills the X server (although the key combination can be disabled<ref>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref>) and can be used to quickly and easily get back to the login prompt.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
- [[Magic SysRq key|Template:Key press]] default sequence for Linux.<ref name="Morton2001">{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref> Not a true C2-compliant SAK.<ref name=":0">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
- Template:Key press then Template:Key press on AIX,<ref>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref> but it can be disabled.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
- Template:Key press for PLATO IV in the 1970s.<ref>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref>
- [[Control-Alt-Delete#Windows NT family|Template:Keypress]] for Windows NT.<ref name=ms-sas/><ref>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref>