Companion virus
Updated: 04/26/2017 by Computer Hope
A companion virus is a computer virus that disguises itself as another file by using the same file name but a different file extension (often .com). By doing so, it can cause a user to accidentally open the virus instead the intended program or document. Upon execution, the virus infects the computer, performing malicious actions such as deleting files from a hard drive.
Companion viruses can be hard to detect as they don't actually modify existing files, which is often a red flag for antivirus programs. The first known companion virus was the Globe virus, detected in 1992.