virus - a piece of programming code usually disguised as something else that causes some unexpected and usually undesirable event. A virus is often designed so that it is automatically spread to other computer users. Generally, there are three main classes of viruses: file infectors, system or boot infectors, and macros viruses.
anti-virus software - a class of program that searches your hard drive and floppy disks for any known or potential viruses.
e-mail virus - malicious computer code sent to you as an e-mail note attachment. The best two defenses against e-mail viruses for the individual user are (1) a policy of never opening an e-mail attachment (even from someone you know) unless you have been expecting the attachment and know what it contains, and (2) installing and using anti-virus software to scan any attachment before you open it.
virus hoax - a false warning about a computer virus. Virus hoaxes are usually forwarded using distribution lists and will typically suggest that the recipient forward the note to other distribution lists. If you get a message about a new virus, you can check it out by going to one of several Web sites that keep up with viruses and virus hoaxes.
trojan horse - a virus in which malicious or harmful code is contained inside apparently harmless programming or data. The term comes from a story in Homer's Iliad that describes how the Greeks presented the citizens of Troy with a large wooden horse during the Trojan War. The Greeks had secretly hidden their warriors in the gift and during the night, the warriors emerged from the wooden horse and overran the city of Troy.
ILOVEYOU virus - an infamous e-mail virus that arrives in a note with "I LOVE YOU" in the subject line and contains an attachment that, when opened, results in the message being re-sent to everyone in the recipient's Microsoft Outlook address book and, perhaps more seriously, the loss of every JPEG, MP3, and certain other files on the recipient's hard disk. The attachment in the ILOVEYOU virus is a Visual Basic Script program.
macro virus - a computer virus that "infects" a Microsoft Word or similar application and causes a sequence of actions to be performed automatically when the application is started or something else triggers it. Macro viruses tend to be surprising but relatively harmless. A typical effect is the undesired insertion of some comic text at certain points when writing a line. Macro viruses are often spread in e-mail.
Chernobyl virus - a computer virus with a potentially devastating payload that destroys all computer data when an infected file is executed. Since many files are executed during computer use, the virus is able to spread quickly and infect those files. The Chernobyl virus is the first virus known to have the power to damage computer hardware. Chernobyl actually is a variant of a virus known as CIH, the initials for the alleged author of the virus, Chen Ing-hau, a Taiwanese computer engineering student.
Kriz virus (known more formally as W32.Kriz, W32.Kriz.dr, or PE_KRIZ)- infects files on Windows 9x and Windows NT and 2000 systems. W32.Kriz is known as a polymorphic virus, meaning it will reside in computer memory until the next time the system is rebooted. The virus overwrites files on the floppy disk drive, hard drive, RAM drive, and network drives. It has a potentially devastating payload that triggers on December 25th of any year once an infected file is run.
worm - a self-replicating virus that does not alter files but resides in active memory and duplicates itself. Worms use parts of an operating system that are automatic and usually invisible to the user. It is common for worms to be noticed only when their uncontrolled replication consumes system resources, slowing or halting other tasks.