Although viruses found in the wild have been limited to personal computer systems, viruses for multi-user systems have been demonstrated in a number of laboratory experiments. Therefore, the potential exists for viruses on multi-user systems. As a result, it is prudent to ensure that the security measures taken on a multi-user system address viruses as well.
Currently, administrators of multi-user systems have a limited number of options for virus protection. Administrators of these systems cannot use monitors or scanners. Since there are no known viruses, there are no signatures to search for or expected virus behavior to detect. An option that is available to administrators of multi-user systems is change detection. Many of these systems are already equipped with a checksum program. Access control shells are another possibility for many systems. Like access control, though, they are not usually designed for virus detection.