During initial days of internet, its use was limited to military and universities for research and development purpose.

Later when all the source is getting integrated then people start to transmit data from one location.

All security threats are intentional i.e. they occur only if intentionally triggered. Security threats can be divided into the following categories:

• Interruption

   

  Interruption is a threat where the resources are being attacked. For example, a user is unable to access its web-server or the web-server is hijacked.

• Privacy-Breach

   

  In this threat, the privacy of user is destroyed. Someone, who is not an authenticated person will access the data of authorized user.

• Integrity

   

  The attacker gets the original data and damage or change it and pass it to the receiver and the original information will be with the intruder not with the receiver.

• Authenticity

   

  This threat occurs when someone try to be the person who he/she is not want to enter into the system by other or someone.