Kill Switch

A kill switch (also called an e-stop) is a security measure used to shut off a device (usually in an emergency situation) in which it cannot be shut down in the usual manner.

Unlike a normal shut down which shuts down all systems naturally in a progressive manner, a kill switch is designed to completely abort the operation at all costs. Often, kill switches are used to protect people from sustaining an injury or being killed, in which case damaging the machine may be considered to be acceptable.

Physical World Applications

Treadmills often use a safety key (essentially a kill switch) that the runner clips to his waist, and if he falls or trips, the safety key is pulled out, and the machine stops immediately.

Computer Software Kill Switch

The concept of "kill switch" may also be applied to software as an "anti-piracy" feature, most notably in "Windows Vista" operating systems. It renders the software essentially useless to users running what is determined by the software author to be an illegitimately obtained, or "pirated", copy.

In the example of Microsoft Windows, the company developed a verification tool named "Windows Genuine Advantage", that originally activated a kill switch, or "reduced functionality mode," on what Microsoft's mandatory software's deemed to be an unlicensed copy of the operating system.

Software kill switches have been shown to have varying degrees of success, as false positives have been known to occur, prompting some vendors like Microsoft to "turn off" the software kill switch in response to market pressure.

There is some anecdotal evidence that some software vendors install kill switches in their software to enforce planned obsolescence, also known as a "forced upgrade". This can cause considerable disruption in said customer's business functions.

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