Security is the degree of protection against danger, damage, loss, and crime. Security as a form of protection is structures and processes that provide or improve security as a condition. Security has to be compared to related concepts: safety, continuity, reliability. The key difference between security and reliability is that security must take into account the actions of people attempting to cause destruction. Perception of security may be poorly mapped to measureable objective security. For example, the fear of earthquakes has been reported to be more common than the fear of slipping on the bathroom floor although the latter kills many more people than the former. Similarly, the perceived effectiveness of security measures is sometimes different from the actual security provided by those measures. The presence of security protections may even be taken for security itself. For example, two computer security programs could be interfering with each other and even cancelling each other's effect, while the owner believes s/he is getting double the protection. Security theater is a critical term for deployment of measures primarily aimed at raising subjective security in a population without a genuine or commensurate concern for the effects of that measure on—and possibly decreasing—objective security. For example, some consider the screening of airline passengers based on static databases to have been Security Theater and Computer Assisted Passenger Prescreening System to have created a decrease in objective security. Perception of security can also increase objective security when it affects or deters malicious behavior, as with visual signs of security protections, such as video surveillance, alarm systems in a home, or an anti-theft system in a car such as a LoJack, signs.

Electrical Power Grid Cyber Security

The federal government of the United States admits that the electric power transmission is susceptible to cyberwarfare. The United States Department of Homeland Security works with industry to identify vulnerabilities and to help industry enhance the security of control system networks, the federal government is also working to ensure that security is built in as the next generation of smart grid networks are developed. In April 2009, reports surfaced that China and Russia had infiltrated the U.S. electrical grid and left behind software programs that could be used to disrupt the system, according to current and former national security officials. The North American Electric Reliability Corporation (NERC) has issued a public notice that warns that the electrical grid is not adequately protected from cyber attack. China denies intruding into the U.S. electrical grid.89 One countermeasure would be to disconnect the power grid from the Internet and run the net with droop speed control only. Massive power outages caused by a cyber attack, could disrupt the economy, distract from a simultaneous military attack, or create a national trauma.