Types of Malware

The term ‘malware’ is short for ‘malicious software’ and is used to describe any piece of software that could be considered harmful or damaging to a computer system.

Many people confuse malware for viruses, but a virus is actually a type of malware. In this blog, we’ll talk you through the most common types of malware and what you can do to prevent falling victim to them.


A virus is a form of malware that inserts itself into computer programmes, files and drives to make copies of itself and spread further. Computer viruses work just like biological ones – it infects ‘cells’ and uses them to reproduce. If a programme on your computer is infected with a virus and you run the programme on another computer, the virus will continue to spread. The effects range from simply causing your computer to crash all the way through to lurking in the background and stealing your personal information.


A Trojan, or Trojan Horse, is a form of malware that disguises itself  as a legitimate programme, acting as a back door for third parties to infiltrate. The name is taken from the Ancient Greek story of the wooden horse used to conceal warriors during the Trojan War.

Trojans are deployed for a number of reasons, including monitoring, data theft and/or corruption and even to download other forms of malware onto the infected system. Essentially, Trojans hide in the background while hackers access your machine.


Ransomware restricts access to your computer until you pay a ransom to the creator(s) of the malware. Some ransomware might ask you to simply pay money before login in order to continue using the computer. This type of ransomware can usually be dealt with by running some antivirus software. Other, more harmful ransomware (remember our blog on Cryptolocker?) actually encrypts your data – failure to pay the ransom will result in the decryption key being destroyed forever, along with your data. This type of ransomware can be catastrophic, so remember to take regular backups!


Just like a virus, a worm works by spreading and replicating itself. Unlike viruses, however, worms spread on their own accord without the need for a human to inadvertedly spread it (i.e. by running an infected programme on another computer).


Like the name suggests, spyware is a type of malware that spies on you. It’s usually used to obtain your data without you knowing, and can be extremely dangerous.

Spyware can also be used for advertising purposes – a piece of software you download may contain spyware that monitors what you browse online – the software’s creator can then sell this information to advertising companies.  Which takes us to the next type…


Adware is used to display adverts on your computer. A lot of software programmes come with their own adverts, and though it isn’t necessarily ‘malicious software’, it can still be annoying and inconvenient.

Adware can be malicious if adverts begin to display on your computer when they shouldn’t – like random pop-ups or a sudden influx of ads on web pages.

Though it can sometimes be impossible to tell whether there is spyware on your system, be selective about what you download online and read the terms and conditions before downloading – yes, it is long and boring, but you might find a clause about allowing your information to be collected.


A keylogger is a form of malware that records all of your keystrokes – passwords, credit card numbers, usernames and other personal information. These keystrokes are then uploaded to a server where they are analysed for useful information. Keyloggers can be very difficult to detect, but there are a number of anti-keylogging programmes that can detect and deal with the issue.


Malware is a pesky devil, but with a little common sense and some solid antimalware software, you can avoid falling prey to it.

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