Security is a system of safeguards designed to protect a computer system and data from intentional and accidental damage or access by unauthorized persons.

How does a computer system detect whether you are the person who should be allowed access to it? Various means have been devised to give access to authorized people. For this, we have four approaches, as discussed below:

  • What  you haveyou may have a key, badge ,token, or plastic card to give you physical access to the locked-up server room or computer building.
  • What you know: Standard user-ids and passwords or some special combination of numbers are given to the users to logon the machine.
  • What you do: Normally, the users put their signatures on the documents to confirm their legitimacy as an authorized user.
  • What you are: Some security measures are biometrics – biological means of identification i.e. fingerprints, voice recognition, eye retina etc.

Virus and Antivirus issues:

To fully understand the concept of a virus (or worm), first recall the concept of a computer program, what can a program do, and how a program is executed? A program is a sequence of instruction given to a computer.

These instructions are for  some sort of processing , By processing we mean performing arithmetic and logical operations on the data in the computer memory , manipulating data in storing and arranging two data item to see if they are equal or not, and transmitting data is sending data from one computer to some other computer on a network or via internet.

A virus is a program that attaches itself with other executable files by modifying them so that the virus program is also loaded and executed with the execution of these programs.

A virus usually perform destructive operation by deleting or modifying (unknowingly) data stored on the storage devices attached to the computer. It is very important to note that a virus is a set of instructions so it cannot physically destroy a hardware (a common misconception).

We can formally describe a virus as “A destructive program containing code that can generate copies of itself and attaches with other program so that it is automatically executed when those programs are executed”.

It is important to know exactly how a virus reaches from one computer to other . As the virus attaches  itself with files present on a system so the only way , a virus can reach from one compute to another , is when some data is exchanged between these computers either though floppy , disks or the network.