Countermeasure (computer)

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

The definition is as IETF RFC 2828[1] that is the same as CNSS Instruction No. 4009 dated 26 April 2010 by Committee on National Security Systems of United States of America.[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 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 explain 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 compromises the confidentiality, integrity or availability properties of resources (potentially different that the vulnerable one) of the organization and others 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, a fire, or a 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]