Viruses and Worms and Trojan Horses - OH MY!

You have probably heard the term 'malware' in recent months. The term malware was derived from 'malicious software' and describes any kind of software created for malicious intent. A common error that people make is to think all types of malware are computer viruses, where in actual fact the exact opposite is true. Computer viruses are just one category out of a whole host of categories listed as malware.

Similarly, worms and Trojan Horses are often mistaken for viruses. There are specific differences between each and I will do my best to straighten out the misconception.

USB Drive

What is a computer virus?

Viruses and Worms and Trojan Horses - OH MY!

A computer virus is a small malicious software program that is typically designed to replicate and attach itself to the executable files of the infected computer. The computer virus can cause damage to the infected computer by deleting or corrupting files and system data or even the wiping the entire hard disk. Computer viruses spread from one computer to another when a user inadvertently shares an infected file with another user via the internet, as an attachment to an email or by means of a removable storage media such as a USB flash drive.

What is a worm?

The difference between a worm and a computer virus is that a worm can propagate without the need to attach itself to an executable file. A worm does not rely on the interaction of a user and exploits vulnerabilities in the security of the host computer. The worm's primary goal is to send copies of itself to any computer it can gain access to. While some worms are fairly harmless to the host machine, there are others designed to deliver a nasty payload. A typical payload would be to create a 'backdoor' to the infected machine which could be used to turn the computer into a zombie and add the computer as a node in a botnet. Botnet's are networks of zombie machines, controlled by the 'zombie master' and are commonly used by people responsible for most of the world's SPAM email.

What is a Trojan Horse?

In much the same way as the mythological Trojan Horse was used as a deceptive means to sneak a small army inside the gates of Troy, in computer terms, a Trojan Horse is software that appears to be legitimate and beneficial to the user, but harbors an unseen danger inside. Once the Trojan Horse has been activated it can delete important system files and cause all kinds of havoc. It can also create a backdoor on the infected machine, turning the computer into a zombie and adding it as a node in a botnet. Trojan Horse's do not replicate or infect files, executable or otherwise.

Viruses and Worms and Trojan Horses - OH MY!