Computer security is a branch of computer technology known as Information Security as applied to computers and networks. The objective of computer security includes protection of information and property from theft, corruption, or natural disaster, while allowing the information and property to remain accessible and productive to its intended users. The term computer system security means the collective processes and mechanisms by which sensitive and valuable information and services are protected from publication, tampering or collapse by unauthorized activities or untrustworthy individuals and unplanned events respectively. The strategies and methodologies of computer security often differ from most other computer technologies because of its somewhat elusive objective of preventing unwanted computer behavior instead of enabling wanted computer behavior. Security Architecture can be defined as the design artifacts that describe how the security controls (security countermeasures) are positioned, and how they relate to the overall information technology architecture. These controls serve the purpose to maintain the system's quality attributes, among them confidentiality, integrity, availability, accountability and assurance. The technologies of computer security are based on logic. As security is not necessarily the primary goal of most computer applications, designing a program with security in mind often imposes restrictions on that program's behavior. There are 4 approaches to security in computing; sometimes a combination of approaches is valid: Trust all the software to abide by a security policy but the software is not trustworthy (this is computer insecurity). Trust all the software to abide by a security policy and the software is validated as trustworthy (by tedious branch and path analysis for example). Trust no software but enforce a security policy with mechanisms that are not trustworthy (again this is computer insecurity). Trust no software but enforce a security policy with trustworthy hardware mechanisms. Many systems have unintentionally resulted in the first possibility. Since approach two is expensive and non-deterministic, its use is very limited. Approaches one and three lead to failure. Because approach number four is often based on hardware mechanisms and avoids abstractions and a multiplicity of degrees of freedom, it is more practical. Combinations of approaches two and four are often used in a layered architecture with thin layers of two and thick layers of four. There are various strategies and techniques used to design security systems. However, there are few, if any, effective strategies to enhance security after design. One technique enforces the principle of least privilege to great extent, where an entity has only the privileges that are needed for its function. That way even if an attacker gains access to one part of the system, fine-grained security ensures that it is just as difficult for them to access the rest. Furthermore, by breaking the system up into smaller components, the complexity of individual components is reduced, opening up the possibility of using techniques such as automated theorem proving to prove the correctness of crucial software subsystems. This enables a closed form solution to security that works well when only a single well-characterized property can be isolated as critical, and that property is also assessable to math. Not surprisingly, it is impractical for generalized correctness, which probably cannot even be defined, much less proven. Where formal correctness proofs are not possible, rigorous use of code review and unit testing represent a best-effort approach to make modules secure. The design should use "defense in depth", where more than one subsystem needs to be violated to compromise the integrity of the system and the information it holds. Defense in depth works when the breaching of one security measure does not provide a platform to facilitate subverting another. Also, the cascading principle acknowledges that several low hurdles does not make a high hurdle. So cascading several weak mechanisms does not provide the safety of a single stronger mechanism. Subsystems should default to secure settings, and wherever possible should be designed to fail secure rather than fail insecure. Ideally, a secure system should require a deliberate, conscious, knowledgeable and free decision on the part of legitimate authorities in order to make it insecure. In addition, security should not be an all or nothing issue. The designers and operators of systems should assume that security breaches are inevitable. Full audit trails should be kept of system activity, so that when a security breach occurs, the mechanism and extent of the breach can be determined. Storing audit trails remotely, where they can only be appended to, can keep intruders from covering their tracks. Finally, full disclosure helps to ensure that when bugs are found the "window of vulnerability is kept as short as possible.

Cyberwarfare

Cyberwarfare refers to politically motivated hacking to conduct sabotage and espionage. It is a form of information warfare sometimes seen as analogous to conventional warfare although this analogy is controversial for both its accuracy and its political motivation.

Cyberwarfare has been defined by government security expert as actions by a nation-state to penetrate another nation's computers or networks for the purposes of causing damage or disruption. The Economist describes cyberwarfare as the fifth domain of warfare, and William J. Lynn, U.S. Deputy Secretary of Defense, states that as a doctrinal matter, the Pentagon has formally recognized cyberspace as a new domain in warfare which has become just as critical to military operations as land, sea, air, and space.

In 2009, President Barack Obama declared America's digital infrastructure to be a strategic national asset, and in May 2010 the Pentagon set up its new U.S. Cyber Command (USCYBERCOM), headed by General Keith B. Alexander, director of the National Security Agency (NSA), to defend American military networks and attack other countries' systems. The United Kingdom has also set up a cyber-security and operations centre based in Government Communications Headquarters (GCHQ), the British equivalent of the NSA. In the U.S. however, Cyber Command is only set up to protect the military, whereas the government and corporate infrastructures are primarily the responsibility respectively of the Department of Homeland Security and private companies. Cyber warfare is the least common type of warfare and has not been used effectively to date.

In February 2010, top American lawmakers warned that the threat of a crippling attack on telecommunications and computer networks was sharply on the rise. According to The Lipman Report, numerous key sectors of the U.S. Economy along with that of other nations are currently at risk, including cyber threats to public and private facilities, banking and finance, transportation, manufacturing, medical, education and government, all of which are now dependent on computers for daily operations. In 2009, President Obama stated that cyber intruders have probed our electrical grids.

The Economist writes that China has plans of winning informationised wars by the mid-21st century. They note that other countries are likewise organizing for cyberwar, among them Russia, Israel and North Korea. Iran boasts of having the world's second-largest cyber-army. James Gosler, a government cybersecurity specialist, worries that the U.S. has a severe shortage of computer security specialists, estimating that there are only about 1,000 qualified people in the country today, but needs a force of 20,000 to 30,000 skilled experts. At the July 2010 Black Hat computer security conference, Michael Hayden, former deputy director of national intelligence, challenged thousands of attendees to help devise ways to reshape the Internet's security architecture, explaining, You guys made the cyberworld look like the north German plain.