Security is the degree of resistance to, or protection from, harm. It applies to any vulnerable and valuable asset, such as a person, dwelling, community, nation, or organization.
As noted by the Institute for Security and Open Methodologies (ISECOM) in the OSSTMM 3, security provides "a form of protection where a separation is created between the assets and the threat." These separations are generically called "controls," and sometimes include changes to the asset or the threat.
Computer security, also known as cybersecurity or IT security, is security applied to computing devices such as computers and smartphones, as well as computer networks such as private and public networks, including the whole Internet. The field includes all five components: hardware, software, data, people, and procedures by which digital equipment, information and services are protected from unintended or unauthorized access, change or destruction, and is of growing importance due to the increasing reliance of computer systems in most societies. It includes physical security to prevent theft of equipment and information security to protect the data on that equipment. Those terms generally do not refer to physical security, but a common belief among computer security experts is that a physical security breach is one of the worst kinds of security breaches as it generally allows full access to both data and equipment.