Stealth viruses must be running to exhibit their stealth qualities. Trojan Horse A program that pretends to have a set of useful or desirable features, but actually contains a damaging payload. VBS programs can be embedded in HTML files and provide active content via the Internet. Since not all content is benign, users should be careful about changing security settings without understanding the implications. Virus A computer program file capable of attaching to disks or other files and replicating itself repeatedly, typically without user knowledge or permission.
Some viruses attach to files so when the infected file executes, the virus also executes.
Other viruses sit in a computer's memory and infect files as the computer opens, modifies or creates the files. Virus Hoaxes Hoaxes are not viruses, but are usually deliberate or unintentional e-messages warning people about a virus or other malicious software program. Some hoaxes cause as much trouble as viruses by causing massive amounts of unnecessary e-mail. If you receive an e-mail message about a virus, check with a reputable source to ensure the warning is real. Sometimes hoaxes start out as viruses and some viruses start as hoaxes, so both viruses and virus hoaxes should be considered a threat.