Countermeasure (computer)

In computer security a countermeasure is an action, device, procedure, or technique that reduces a threat, vulnerability, or attack, eliminating or preventing it by minimizing the harm it can cause. It can also include discovering and reporting vunerabilities so that corrective action can be taken.

The definition is given in IETF RFC 2828^[1] and CNSS Instruction No. 4009 dated 26 April 2010 by the Committee on National Security Systems.^[2]

According to the Glossary^[3] by InfosecToday, the meaning of countermeasure is:

The deployment of a set of security services to protect against a security threat.

A synonym is security control.^[2][4] In telecommunications, communication countermeasures are defined as security services as part of the OSI Reference model by ITU-T X.800 Recommendation. X.800 and ISO ISO 7498-2 (Information processing systems – Open systems interconnection – Basic Reference Model – Part 2: Security architecture are technically aligned.

The following picture explains the relationships between these concepts and terms:

      + - - - - - - - - - - - - +  + - - - - +  + - - - - - - - - - - -+
      | An Attack:              |  |Counter- |  | A System Resource:   |
      | i.e., A Threat Action   |  | measure |  | Target of the Attack |
      | +----------+            |  |         |  | +-----------------+  |
      | | Attacker |<==================||<=========                 |  |
      | |   i.e.,  |   Passive  |  |         |  | |  Vulnerability  |  |
      | | A Threat |<=================>||<========>                 |  |
      | |  Agent   |  or Active |  |         |  | +-------|||-------+  |
      | +----------+   Attack   |  |         |  |         VVV          |
      |                         |  |         |  | Threat Consequences  |
      + - - - - - - - - - - - - +  + - - - - +  + - - - - - - - - - - -+

A resource (both physical or logical) can have one or more vulnerabilities that can be exploited by a threat agent in a threat action. The result can potentially compromise the confidentiality, integrity or availability properties of these resources (potentially different than the vulnerable one) of the organization and other involved parties (customers, suppliers).
The so-called CIA triad is the basis of information security.

The attack can be active when it attempts to alter system resources or affect their operation: so it compromises integrity or availability. A "passive attack" attempts to learn or make use of information from the system but does not affect system resources, compromising confidentiality.

A threat is a potential for violation of security, which exists when there is a circumstance, capability, action, or event that could breach security and cause harm. That is, a threat is a possible danger enabling the exploitation of a vulnerability. A threat can be either "intentional" (i.e., intelligent; e.g., an individual cracker or a criminal organization) or "accidental" (e.g., the possibility of a computer malfunctioning, or the possibility of an "act of God" such as an earthquake, fire, or tornado).^[1]

A set of policies concerned with information security management, the information security management systems (ISMS), has been developed to manage, according to risk management principles, the countermeasures in order to accomplish to a security strategy set up following rules and regulations applicable in a country.^[4]