Is there really a virus problem?
In 1995, Ernst & Young released a security survey that showed that 67% of companies had virus attacks during the year. This was a rise from 54% in 1994. The cost of each virus attack has been estimated, by a British magazine, at over $13,000 (Ł8,000, according to exchange rates on August 4, 1997). With the number of reported cases rising and the cost so high, it is essential to understand the virus problem better and to put the solutions to work in the marketplace. In January 1997, the NCSA (National Computer Security Association) reported approximately 200 macro viruses had been discovered. In just six months, the number has increased by almost 300%. It is now estimated that over 90% of all companies have at least one macro virus resident somewhere in their computing systems (source: Applied Technologies Group). What is a virus?
A virus is simply a self-replicating program. It is important to distinguish between viruses and "Trojan Horses". A virus is just a program that copies itself; it does not have to be destructive in anyway. A "Trojan Horse" is a deliberately destructive program, but does not replicate. There are other programs, such as jokes and droppers, that are not viruses, but many anti-virus programs give the option to the user, if he/she wants to search for these programs. Another important distinction is the one between "bugs" and viruses. Programs occasionally have "bugs" in them. They are only programming errors (though the programmer won’t like admitting to it.)
What is so terrible about viruses?
Viruses will usually do nothing more than irritate the user of the infected computer. At the least, they will take up much-needed hard disk space. But, as some can be destructive to the infected host, it is always a good idea to have anti-virus protection. People have various reasons for wanting to remove the viruses from their computer. First, 5% of viruses are destructive. Second, since almost 100% of those viruses found "in-the-wild", or in public circulation, are memory-resident, there will be conflicts with other programs the user will want to run. Third, the anxiety the user may have that the particular virus that he/she has is a different mutation of the documented virus. What is a typical virus?
There are no typical viruses. Viruses can be categorized into a few different groups: file viruses, boot viruses, multi-partite viruses, stealth viruses, polymorphic viruses, and macro viruses.