On March 26, 1999, people everywhere began sending Microsoft and anti-virus companies information about something going wrong with their computers. Those companies figured out that it was a macro virus called Melissa hidden into a plain email letter. It would make the infected computers email program send an email saying it was an important message from the sender. Thousands of people were infected worldwide. One commonly asked question about computers is what are computer viruses? Another popular question is how do I prevent viruses from infecting my computer? These questions are answered in this essay. While there is no widely accepted definition of the term computer virus, one definition would be executable code that, when run by someone, infects or attaches itself to other executable code in a computer in an effort to reproduce it. Some computer viruses are malicious, erasing files or locking up systems. Others merely present a problem completely through the act of infecting other code (Mansfield 31). Closely related to computer viruses are Trojan Horses and Worms. A Trojan Horse is a program that performs some unwanted action while pretending to do something else to avoid suspicion. One common class of Trojan Horses is a fake login program that collects accounts and passwords by prompting for this info just like a normal login program does. Another is a fake disk defragmenter that erases files rather than reorganizing them. A Trojan Horse differs from a virus because the Trojan Horse does not attempt to reproduce itself like a virus. A Worm is the same as a virus except it also tries to spread itself over the Internet or a network (internet).Some of the types of viruses and other destructive code are file infectors, cluster infectors, macro viruses, and system infectors (internet).File infectors are viruses that attach themselves to regular programs, such as .COM or .EXE files under DOS. That means they are put into action ...
