Additional Authentication Information
In addition to the name and password, we can use other information available to authenticate users. Suppose Adams works in the accounting department during the shift between 8:00 a.m. and 5:00 p.m., Monday through Friday. Any legitimate access attempt by Adams should be made during those times, through a workstation in the accounting department offices. By limiting Adams to logging in under those conditions, the system protects against two problems:
Someone from outside might try to impersonate Adams. This attempt would be thwarted by either the time of access or the port through which the access was attempted.
Adams might attempt to access the system from home or on a weekend, planning to use resources not allowed or to do something that would be too risky with other people around.
Limiting users to certain workstations or certain times of access can cause complications (as when a user legitimately needs to work overtime, a person has to access the system while out of town on a business trip, or a particular workstation fails). However, some companies use these authentication techniques because the added security they provide outweighs inconveniences.
Using additional authentication information is called multifactor authentication. Two forms of authentication (which is, not surprisingly, known as two-factor authentication) are better than one, assuming of course that the two forms are strong. But as the number of forms increases, so also does the inconvenience. (For example, think about passing through a security checkpoint at an airport.) Each authentication factor requires the system and its administrators to manage more security information.