In a common sense, security is freedom from any risk or danger. In context of computer science, security is prevention of or protection against;
• Access to information by unauthorized people
• Unauthorized destruction or alteration of that information.
In other words, a secure system is a system on which enough trust can be put to use it together with sensitive information. Computer Security is frequently associated with three core of areas;
a). Confidentiality: Ensuring that the data cannot be accessed by unauthorized persons.
b). Integrity: Ensuring that information is not altered by unauthorized person in a way that is not detectable by authorized persons.
c). Authentication: Ensuring the users are the person they claim to be.
Computer Security is also defined as :
a). Physical Security: Controlling the coming and outgoing of people and materials, protection against the elements and manuals disasters.
b). System Security: User access and authentication controls, maintaining file and file system integrity, make backups, log keeping and auditing.
c). Personal Security: Hiring employee to background screening, monitoring and handling departure of persons.
d). Network Security: Protecting network and telecommunication equipment, controlling access from un-trusted.