Malware

What it is

'Malware' is any kind of malicious software designed to damage or harm a computer system. Malware aims to gain access to your computer without you knowing it's there. It’s generally used:

• to get access to, and control of, a computer system
• for profit
• to steal sensitive information from an individual or business
• to blackmail someone.

How it works

Malware can enter your computer system when you download an infected file or visit an untrustworthy website. It's usually attached to files you:

• get in an email
• download from the internet
• get on a portable drive, like a USB drive.

When malware gets into your computer it can spread through your programs and files, corrupting them and causing your computer to either slow down or stop working. Having malware in your computer system can make it more vulnerable to other attacks, like ransomware.

Common types of malware

The first kind of malware most people think of is a virus. But, there are other common types of malware to be aware of.

Worms

Worms are a kind of malware that can enter your computer system through:

• a network like the internet
• your local network
• portable media like USB drives.

Worms can replicate themselves, and once they’re in your system they can move quickly and easily through lots of computers on a network. Worms can also damage your files and programs, and leave you vulnerable to other forms of attack.

Trojans

Just like the Trojan horse of Troy, this malware hides inside legitimate objects — for example, files like Word documents or PDFs — until someone opens them. When Trojans get into your system, they can give others access to your computer without your knowledge. Unlike worms, they can't replicate themselves. They need human interaction to spread.

If other people get access to your computer they can download more malware, like worms, from the internet. Trojans themselves don’t spread over networks, but the other malware they download can.

Spyware and adware

Spyware and adware work by passing information to third parties about your behaviour online. This allows them to target you with advertising for products and services, whether you’re interested in them or not. Some of this content can be offensive, which can be a clue that you have spyware or adware on your computer.

Adware monitors the websites you visit and pushes ads onto your device. It can choose ads that you’re likely to click on, or ads that would embarrass you. These ads can appear within a site or as popup windows. Adware can cause problems when:

• popup windows become difficult to dismiss or close
• information is gathered and passed on to others without asking for your consent
• it slows your internet browser or computer down
• it contains objectionable material.

Spyware gathers information about the system it infects. It:

• tracks your activity
• monitors the websites you visit, and
• passes this information on to others without your consent.

It can even track the information you type into websites. In some cases, this means that personal or sensitive information — like your internet banking details — can be accessed and used without your knowledge or consent. This is called keylogging.