What is the difference between a virus, a worm, and a Trojan Horse?
• File-Infecting Viruses – This is the most common type of virus. A file-infecting virus attaches itself to an executable program file by adding its own code to the file. An executable program file can be run like any other program, and has an .EXE extension (i.e. in the filename virus.exe, the .exe is the extention). The virus code is usually added in such a way that it escapes detection. When the infected file is run, the virus can attach itself to other executable files. Files infected by this type of virus usually have a .COM, .EXE, or .SYS extension. Damage to data occurs when the virus is triggered. A virus can be triggered when an infected file is executed, or when a particular environment setting is met (such as a specific system date). • Trojan Horse Programs – A Trojan horse program disguises itself as a legitimate program such as a game or utility, but once it is executed, it can destroy or scramble data. A Trojan horse program can contain viruses, but is not a virus itself.
