You will need to remind yourself of the security issues and solutions in this section.

One of the tasks of the Operating System is to keep account of all users and the resources they needed. This is particularly important in a multi-access or network system. If there is a breach of security then it should be possible to track down the user who did it - there should be a log of who used the system and when.

The Operating System also needs to control security measures such as checking passwords and only allowing access to parts of the system to those with the appropriate security level.

If a user dials in on a WAN and logs in to use a computer system, a dial-back system might be used where the connection is cut, and the OS dials back the user to make sure someone else has not used a stolen password.