{{Short description|Special key combination}} A '''secure attention key''' ('''SAK'''), '''special attention key''',<ref>{{Cite web|url=https://mastodon.social/@pid_eins/113441346864726148|title=Lennart Poettterin on Mastodon|author=Lennart Poettering|date=2024-11-07|accessdate=2025-03-26}}</ref> or '''secure attention sequence''' ('''SAS''')<ref name=ms-sas>{{Cite web|url=https://learn.microsoft.com/en-us/windows/win32/secgloss/s-gly#_SECURITY_SECURE_ATTENTION_SEQUENCE_GLY|title=S (Security Glossary) - Win32 apps {{!}} Microsoft Learn|author=Microsoft|date=7 January 2021 |access-date=2023-04-02}}</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: * {{key press|Ctrl|Alt|Shift|Esc}}: Introduced in systemd v257 as a more reliable SAK for Linux distributions but may require support from the currently running desktop environment.<ref>{{Cite web|url=https://mastodon.social/@pid_eins/113441386934639615|title=Lennart Poettterin on Mastodon|author=Lennart Poettering|date=2024-11-07|accessdate=2025-03-26}}</ref> It is implemented as of gdm (GNOME display manager) 47.<ref>{{Cite web|url=https://gitlab.gnome.org/GNOME/gdm/-/commit/969ffab4855b12d6901fc06d1a844583f294fb50|title= 47.rc|author=Ray Strode|date=2024-09-11|accessdate=2025-03-26}}</ref> * {{key press|Ctrl|Alt|Backspace}} on X Window System immediately kills the X server (although the key combination can be disabled<ref>{{Cite web|url=https://wiki.ubuntu.com/XorgCtrlAltBackspace|title=XorgCtrlAltBackspace|author=dhcp198-158|date=2010-06-12|accessdate=2025-03-26}}</ref>) and can be used to quickly and easily get back to the login prompt.<ref>{{Cite web|url=https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/7/html/desktop_migration_and_administration_guide/enable-ctrl-alt-backspace#enable-ctrl-alt-backspace|title=Enabling the Ctrl+Alt+Backspace Shortcut|accessdate=2025-03-26}}</ref> * {{key press|Alt|SysRq|K}} default sequence for Linux.<ref name="Morton2001">{{cite web|url=https://www.kernel.org/doc/Documentation/SAK.txt|title=Linux 2.4.2 Secure Attention Key (SAK) handling|author=Andrew Morton|author-link=Andrew Morton (computer programmer)|date=2001-03-18|publisher=Linux Kernel Organization|accessdate=2011-05-30}}</ref> Not a true C2-compliant SAK.<ref name=":0">{{cite web | url=https://www.kernel.org/doc/html/latest/admin-guide/sysrq.html | title=Linux Magic System Request Key Hacks | date=2013-08-12 | publisher=kernel.org | accessdate=2017-05-21 }}</ref> * {{key press|Ctrl|X}} then {{key press|Ctrl|R}} on AIX,<ref>{{Cite web|url=https://www.ibm.com/docs/en/aix/7.3?topic=options-using-secure-attention-key|title=Using the Secure Attention Key|author=IBM|website=IBM |date=2025-02-03|accessdate=2025-03-26}}</ref> but it can be disabled.<ref>{{Cite web|url=https://www.ibm.com/docs/en/aix/7.3?topic=options-configuring-secure-attention-key|title=Configuring the Secure Attention Key|author=IBM|website=IBM |date=2025-02-03|accessdate=2025-03-26}}</ref><ref>{{Cite web|url=https://www.ibm.com/docs/en/sig-and-i/10.0.2?topic=information-aix-default-attributes|title=AIX Default Attributes|author=IBM|website=IBM |date=2025-02-20|accessdate=2025-03-26}}</ref> * {{key press|Shift|Stop}} for PLATO IV in the 1970s.<ref>{{Cite web|url=http://www.bitsavers.org/pdf/cdc/plato/97405900C_PLATO_Users_Guide_Apr81.pdf|title=PLATO User's Guide|author=Control Data Corporation|date=1981-04-30|accessdate=2023-04-21}}</ref> * {{Keypress|Ctrl|Alt|Delete}} for Windows NT.<ref name=ms-sas/><ref>{{Cite web|url=https://networkencyclopedia.com/secure-attention-sequence-sas/|title=Secure Attention Sequence (SAS) - Network Encyclopedia|date=6 January 2020 |access-date=2023-04-02}}</ref>
==See also== * Control-Alt-Delete * Magic SysRq key * Break key
==References== {{Reflist}}
{{DEFAULTSORT:Secure Attention Key}} Category:Computer security procedures Category:Computer access control
{{desktop-environment-stub}}