A secure attention key (SAK) or secure attention sequence (SAS) is a special key or
key combination
computing, a keyboard shortcut also known as hotkey is a series of one or several keys to quickly invoke a software program or perform a preprogrammed action. This action may be part of the standard functionality of the operating system or ...
to be pressed on a
computer keyboard
A computer keyboard is a peripheral input device modeled after the typewriter keyboard which uses an arrangement of buttons or keys to act as mechanical levers or electronic switches. Replacing early punched cards and paper tape technolog ...
before a
login
In computer security, logging in (or logging on, signing in, or signing on) is the process by which an individual gains access to a computer system by identifying and authenticating themselves. The user credentials are typically some fo ...
screen which must, to the user, be completely trustworthy. The
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
kernel
Kernel may refer to:
Computing
* Kernel (operating system), the central component of most operating systems
* Kernel (image processing), a matrix used for image convolution
* Compute kernel, in GPGPU programming
* Kernel method, in machine learn ...
, 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
Login spoofings are techniques used to steal a user's password. The user is presented with an ordinary looking login prompt for username and password, which is actually a malicious program (usually called a Trojan horse) under the control of the ...
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.
*
default sequence for
Linux
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, whi ...
.
Not a true
C2-compliant SAK.
See also
*
Control-Alt-Del
*
Magic SysRq key
The magic SysRq key is a key combination understood by the Linux kernel, which allows the user to perform various low-level commands regardless of the system's state. It is often used to recover from freezes, or to reboot a computer without corr ...
*
Break key
The Break key (or the symbol ⎉) of a computer keyboard refers to breaking a telegraph circuit and originated with 19th century practice. In modern usage, the key has no well-defined purpose, but while this is the case, it can be used by softwar ...
References
Computer security procedures
Computer access control
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