A code segment which replicates by attaching copies of itself to existing executables. The new copy of the virus is executed when a user executes the new host program. For example, some viruses display a text string on a particular date. There are many types of viruses including variants, overwriting, resident, stealth, and polymorphic. Consider as an example an editing program for a multi-user system.
Worms commonly utilize network services to propagate to other host systems.
The number of known viruses is increasing, and the rate of virus incidents is growing moderately. Most organizations use anti- virus software and other protective measures to limit the risk of virus infection. In some instances, threats posed by foreign government intelligence services may be present. In addition to possible economic espionage, foreign intelligence services may target unclassified systems to further their intelligence missions. The accumulation of vast amounts of electronic information about individuals by the government, credit bureaus, and private companies combined with the ability of computers to monitor, process, aggregate, and record information about individuals have created a very real threat to individual privacy.