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Most people understand that computers can get viruses – that interrupt the computers activities and usually cause harm to the computer in some way even causing the computer to become unusable.

But there are a wide variety of things that can infect a computer and potentially cause harm that are not classed as viruses.   These include ransomware, Trojans, spyware and PUPS.

Malware, short for malicious software, is any software used to disrupt computer systems, gather sensitive information, gain access to private computer systems, or display unwanted advertising. Malware is defined by its malicious intent and does not include software that causes unintentional harm.


Ransomware pops up a message on screen demanding payment or else the computer will be rendered unusable or that the contents have been encrypted and can only be decrypted on payment. This can be a substantial sum of money.  On payment,  the fraudster may provide the decryption key or may not.  


Trojan horse or Trojan, is any malicious computer program which misrepresents itself to appear useful.  It stays quiet unless the payload is due to be delivered.

Trojans are generally spread by a user being tricked into opening an e-mail attachment that appears harmless e.g. an invoice or a list of songs.  The payload can be anything, but the most common is the creation of a backdoor through the security. This information is passed to a controller which can then have unauthorised access to the affected computer.

Unlike computer viruses, Trojans generally do not attempt to propagate themselves.


These are programmes designed to track the user’s browsing history, display unsolicited advertisements. Spyware programmes do not spread like viruses; instead they are generally installed by exploiting security holes. They can also be hidden and packaged together with unrelated user-installed software.

Spyware or other malware is sometimes found embedded in programmes supplied officially by companies. These  appear useful, but may have  hidden tracking functionality that returns data to the makers.  


PUPS stands for Potentially Unwanted Programmes.  This is software that is potentially not wanted by the user but was installed unintentionally – usually as part of another installation. These programmes usually just track usage of the computer and report it back to their creator. That information is then used to analyse the user’s regular websites, adverts viewed, purchases made etc.

Is Malware Easy to Find?

Malware is often designed to hide from scans by anti-malware.

This can be through a combination of techniques designed to avoid detection and analysis, including:--

·         Confusing the detection methods used by the anti-malware tools. E.g. by changing the server used by the malware.

·         The malware may run only at certain times or following certain actions taken by the user and stay dormant the rest of the time.

Security Loopholes

Much package software has loopholes i.e. security holes that can be exploited by malware. This can be common products such as Word Processing but it also applies to plugins for your browser, APPS and anything that contains programming code. It is almost impossible to write any piece of software without potential loopholes and most makers regularly issue updates that close known security holes. It is important o keep your software up to date.

Anti-malware strategies

Anti-malware programmes provide protection through preventing infection by the malware and by scanning to detect and remove malware.  Both elements are essential.


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