ALERT

[WEBINAR] See the Whole Story: The Case for a Visualization Platform

Companion Virus

Definition - What does Companion Virus mean?

A companion virus is a complicated computer virus which, unlike traditional viruses, does not modify any files. Instead, it creates a copy of the file and places a different extension on it, usually .com. This unique quality makes a companion virus difficult to detect, as anti-virus software tends to use changes in files as clue.

The companion virus is an old type of virus that was more prominent during the MS-DOS era. It is propagated mostly through human intervention.

Techopedia explains Companion Virus

When the user executes a program with the command prompt, he or she usually types in the name of the program. Because MS-DOS does not need a specification of the file type, it automatically runs the first file name that matches what the user types. So, if a companion virus copies file.exe and renames it file.com, because file.com comes before file.exe, MS-DOS will run that first program, thus spreading the infection in the computer, unbeknownst to the user.

Companion viruses mostly need human intervention to further infect a computer and with the advent of Windows XP, which does not use the MS-DOS interface much anymore, there were fewer ways for this type of virus to propagate itself. However, it can still work if a user double clicks it unintentionally or is run by accident, especially if the “show file extensions” option is not activated.

Connect with us

Techopedia on Linkedin
Techopedia on Linkedin
Tweat cdn.techopedia.com
"Techopedia" on Twitter


'@Techopedia'
Sign up for Techopedia's Free Newsletter!

Email Newsletter

Join thousands of others with our weekly newsletter

Resources
Free Whitepaper: The Path to Hybrid Cloud
Free Whitepaper: The Path to Hybrid Cloud:
The Path to Hybrid Cloud: Intelligent Bursting To Amazon Web Services & Microsoft Azure
Free E-Book: Public Cloud Guide
Free E-Book: Public Cloud Guide:
This white paper is for leaders of Operations, Engineering, or Infrastructure teams who are creating or executing an IT roadmap.
Free Tool: Virtual Health Monitor
Free Tool: Virtual Health Monitor:
Virtual Health Monitor is a free virtualization monitoring and reporting tool for VMware, Hyper-V, RHEV, and XenServer environments.
Free 30 Day Trial – Turbonomic
Free 30 Day Trial – Turbonomic:
Turbonomic delivers an autonomic platform where virtual and cloud environments self-manage in real-time to assure application performance.