Embedded code or device, usually in software, that disables the software when the license is no longer valid. Lockout devices are often used on mainframe software, which is essentially leased; typically, if the software vendor does not suspend the lockout periodically, the software is disabled. Similarly, some software samples are provided under a license, which allows a fixed period of use or fixed number of users. At the end of this period an unlocking key must be entered or the lockout device takes effect.
Lockout devices are potentially illegal and may in some jurisdictions give rise to criminal or tort liability, if the licensee is not informed of their presence and effect. It is also highly inadvisable to use lockout software in mission critical or safety applications. The lockout function should not normally be used if there is a dispute about license terms, rather than a clear violation, since this might in some jurisdictions give rise to serious legal liability.