Defense strategy (computing)

In computing, defense strategy is a concept and practice used by computer designers, users, and IT personnel to reduce computer security risks. Boundary protection employs security measures and devices to prevent unauthorized access to computer systems (referred to as controlling the system border). The approach is based on the assumption that the attacker did not penetrate the system. Examples of this strategy include using gateways, routers, firewalls, and password checks, deleting suspicious emails/messages, and limiting physical access. Boundary protection is typically the main strategy for computing systems; if this type of defense is successful, no other strategies are required. This is a resource-consuming strategy with a known scope. External information system monitoring is part of boundary protection. Information System Monitoring employs security measures to find intruders or the damage done by them. This strategy is used when the system has been penetrated, but the intruder did not gain full control. Examples of this strategy include antivirus software, applying a patch, and network behavior anomaly detection. This strategy's success is based on competition of offence and defence. This is a time and resource-consuming strategy, affecting performance. The scope is variable in time. It cannot be fully successful if not supported by other strategies. Unavoidable actions employ security measures that cannot be prevented or neutralized. This strategy is based on the assumption that the system has been penetrated, but an intruder cannot prevent the defensive mechanism from being employed. Examples of this strategy include rebooting, using physical unclonable functions, and using a security switch. Secure enclave is a strategy that employs security measures that prevent access to some parts of the system. This strategy is used when the system has been penetrated, but an intruder cannot access its special parts. Examples of this strategy include using the Access level, using a Trusted Platform Module, using a microkernel, using Diode (unidirectional network device), and using air gaps.