The foundation of most user access control is good password control. Historically, simple password schemes and physical control of network resources were enough to provide reasonable security So long as users need physical access to computers and network resources, good building security and simple password schemes are often safe enough. In recent years, the need to support dial-up computer access to remote and mobile users has necessitated the use of more sophisticated security systems. Many companies do not change default passwords before a computer goes into operation. Attackers know default passwords and use them if they have not been changed.
Attackers use automated tools to detect newly-connected computers on the Internet.
Within minutes of the coming up on the Internet for the first time, attackers can detect the computer and attempt to log on to it using default passwords. This is an extremely dangerous situation. Although the attacker can no longer use a default password to log on to the computer, he still has access through his own back door. It also prevents attackers from intercepting and disrupting communication streams, and engaging in fraudulent transactions. Authentication technologies use and extend cryptography systems to prevent the misuse of computer network resources.