Malware is short for malicious software. It is any kind of unwanted software that is installed on your device (pc, tablet, mobile phone) without your permission or without you even knowing it. Malware can also be distributed through USB sticks so as a rule you should never use USB sticks that you find or borrow from friends or colleagues.
Malware is designed to damage or disrupt a system. It can also be used to give an online criminal control over a device or to steal personal information.
Examples of malware: virus, worms, Trojan horses.