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What Is Security and Resilience?

It is the Department of Homeland Security’s responsibility to enhance the security and resilience of the nation’s critical infrastructure. But what is security and resilience?


Presidential Policy Directive 21 (PPD-21): Critical Infrastructure Security and Resilience defines security as reducing the risk to critical infrastructure by physical means or defense cyber measures to intrusions, attacks, or the effects of natural or manmade disasters.

Examples of security measures:

  • Badge entry at doors
  • Using antivirus software
  • Fencing around buildings
  • Locking computer screens


PPD-21 defines resilience as the ability to prepare for and adapt to changing conditions and withstand and recover rapidly from disruptions. Resilience includes the ability to withstand and recover from deliberate attacks, accidents, or naturally occurring threats or incidents.

Examples of resilience measures:

  • Developing a business continuity plan
  • Having a generator for back-up power
  • Using building materials that are more durable
Last Published Date: July 12, 2017

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