Security is being free from danger. The term can be used with reference to crime, accidents of all kinds, etc. Security is a vast topic including security of countries against terrorist attack, security of computers against hackers, home security against burglars and other intruders, financial security against economic collapse and many other related situations.

Security is the condition of being protected against danger or loss. In the general sense, security is a concept similar to safety. The nuance between the two is an added emphasis on being protected from dangers that originate from outside. Individuals or actions that encroach upon the condition of protection are responsible for the breach of security.

Security has to be compared and contrasted with other related concepts: Safety , continuity , reliability . The key difference between security and reliability is that security must take into account the actions of active malicious agents attempting to cause destruction.
Factors that must be considered befor buing an security device are:
1. Reliability
2. Effectiveness
3. Price
4. Maintenance
5. Ease of use (workability, i.e. security tag remover)