E8) Can mainframe computers be susceptible to computer viruses?

Yes.  Numerous experiments have shown that computer viruses spread
very quickly and effectively on mainframe systems.  However, to our
knowledge, no non-research computer virus has been seen on mainframe
systems.  (The Internet worm of November 1988 was not a computer virus
by most definitions, although it had some virus-like characteristics.)

Computer viruses are actually a special case of something else called
"malicious logic", and other forms of malicious logic -- notably
Trojan horses -- are far quicker, more effective, and harder to detect
than computer viruses.  Nevertheless, on personal computers many more
viruses are written than Trojans.  There are two reasons for this:
(1) Since a virus propagates, the number of users to which damage can
be caused is much greater than in the case of a Trojan; (2) It's
almost impossible to trace the source of a virus since viruses are
not attached to any particular program.

For further information on malicious programs on multi-user systems,
see Matt Bishop's paper, "An Overview of Malicious Logic in a Research
Environment", available by anonymous FTP on Dartmouth.edu
(129.170.16.4) as "pub/security/mallogic.ps".


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