{{Primary sources, date=December 2013
Intrusion tolerance is a
fault-tolerant design
Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of one or more faults within some of its components. If its operating quality decreases at all, the decrease is proportional to the ...
approach to defending information systems against malicious attacks. In that sense, it is also a
computer security
Computer security, cybersecurity (cyber security), or information technology security (IT security) is the protection of computer systems and networks from attack by malicious actors that may result in unauthorized information disclosure, t ...
approach. Abandoning the conventional aim of preventing all intrusions, intrusion tolerance instead calls for triggering mechanisms that prevent intrusions from leading to a system security failure. There are two major variants of intrusion tolerance mechanisms: mechanisms based on redundancy (e.g., as in Byzantine fault tolerance); mechanisms based on intrusion detection (e.g., with an
intrusion detection system
An intrusion detection system (IDS; also intrusion prevention system or IPS) is a device or software application that monitors a network or systems for malicious activity or policy violations. Any intrusion activity or violation is typically rep ...