The IT Law Wiki



Fault tolerance refers to:

[a]ttributes of software that bear on its ability to maintain a specified level of performance in case of software faults or of infringement of its specified interface.[1]


Fault tolerance is:

the ability of a system to respond gracefully to an unexpected hardware or software failure.[2]
[t]he capability of a computer system, after any malfunction of any of its hardware or 'software' components, to continue to operate without human intervention, at a given level of service that provides: continuity of operation, data integrity, and recovery of service within a given time.[3]
1. The ability of a system or component to continue normal operation despite the presence of hardware or software faults. 2. The number of faults a system or component can withstand before normal operation is impaired. 3. Pertaining to the study of errors, faults, and failures, and of methods for enabling systems to continue normal operation in the presence of faults.[4]


Fault tolerance is generally focused on mitigating the impacts of non-malicious events such as accidents and random failures. New principles need to be added to the concept in order to develop systems that are resilient in the face of malicious activity and hostile attacks. In a highly distributed system environment such as the Internet, component and node failures are common. Resilient systems (also referred to as “fail-secure” systems in the context of IT security) that retain their security properties amid component failures could mitigate potential risks that may arise as a result of such failures. Systems designed to maintain predictable timeliness properties must also be resilient against denial of service attacks and disruption of system resources.


  1. ISO/IEC Standard 9126 (1991), revised by ISO/IEC 25010:2011.
  2. Technology Assessment: Cybersecurity for Critical Infrastructure Protection, at 200 n.21.
  3. U.S. Export Administration Regulations, Part 772 (15 C.F.R. §772.1).
  4. IEEE, IEEE Standard Glossary of Software Engineering Terminology (IEEE Std 610.12-1990) (1990) (full-text).