Personal computers have been immune to worms because they are single task systems. The increasing functionality of personal computer operating systems will soon change this. Personal computers will become true multi-tasking systems, and will inherit both the functionality and security vulnerabilities that those systems have exhibited.
Multi-user systems have never been attractive virus targets, due to limited population, low software interchange rates, and because they use some form of access control. The advent of 486-class PCs is likely to change this. In addition to the increased performance of PC based machines, the UNIX workstation market is growing rapidly, producing high-performance machines at extremely affordable prices. Multi-user systems will be gaining market share, increasing their attractiveness to virus authors.
This large homogeneous population of multi-user systems will be an attractive target for both virus authors and worm developers. Personal computer worms or virus/worm hybrids may become the new threat the 90s. With a large homogeneous population of systems available, it is conceivable that authors of malicious code will combine the previously disjoint attacks of viruses and worms. An attack consisting of a worm traversing a network and dropping viruses on the individual hosts becomes a startling possibility.
As the functionality of personal computers continues to grow, new types of tools will be required to achieve the same degree of security. Scanners must be supplemented with configuration review tools. Identification &authentication tools (non-existent or neglected on most PCs) will become an important security tool on personal computers. Intrusion detection tools may become applicable to personal computers. Change detection will also play an increased role.
Administrators of personal computer networks must become familiar with a new set of practices, tools, and techniques, such as firewalls. They will need to draw upon the world of multi-user systems for this knowledge.
As the differences between PC and multi-user environments decreases, the likelihood of these environments facing similar threats will increase. Viruses will be more likely in the multi-user world; worms will become a threat in personal computer networks.