What Exactly Is Malware?

The term ‘malware’ has been derived from a combination of two words – malicious + software.

Malware refers to any piece of software that has been developed with the express intention of doing harm in some way.


Typically, malware is classified according to how it is spread, what it’s function is or how it is executed.

The main types of malware are as follows –

  • Viruses
  • Worms
  • Spyware
  • Trojans
  • Backdoors


A large amount of malware gets lumped into the category of being a virus, sometimes quite erroneously, because of the fact that viruses were the first type of malware to appear.

That misconception has perpetuated over the years as the popular media tend not to know the difference between different types of malware and also because viruses have become more sophisticated and often include other nasty surprises in their payload.

Viruses work and spread within an infected system by attaching themselves to files and are executed when those files are opened.

Viruses spread between other computers by travelling across networks, via email attachments and also via external drives.


Computer worms are similar to viruses in many respects but differ in that they do not require other pieces of software to attach themselves to.

A worm will modify the operating system on the computer that they have infected  in order to become part of the boot process.

Worms spread either by tricking people into installing them, often via social engineering techniques, or by exploiting some sort of vulnerability in the target system.


Spyware refers to software that collects and sends information back to their source.

This information is normally based around the users surfing habits but can also be somewhat more malicious when the data being transferred includes details such as credit card numbers.

Spyware normally finds it’s way onto systems via deception in that it will come bundled with other useful programs that the user may wish to install.


Trojan horses are similar to viruses in so much that they get executed by being part of an otherwise useful piece of software.

Unlike viruses, however, Trojan horses remain attached to the software they came bundled with and cannot infect other files.

Therefore, Trojans spread by tricking downloaders into downloading the host file that they are attached to which is why torrent downloads, for example, can carry some risk.


A backdoor is a small piece of software that allows the controller to access a computer system remotely without having to pass any of the normal authentication procedures.

There are two types of backdoor, the first of which are installed by a Trojan and the second which are spread via worms.

Backdoors offer the programmer the opportunity to access the target system, often leading to further trojans and other infections being manually added.

About Lee Munson

Lee's non-technical background allows him to write about internet security in a clear way that is understandable to both IT professionals and people just like you who need simple answers to your security questions.


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