Malware is software designed to harm a device and/or network. As Cisco defines it:

"Malware is developed as harmful software that invades or corrupts your computer network. The goal of malware is to cause havoc and steal information or resources for monetary gain or sheer sabotage intent."

The term malware is an umbrella term for a variety of attack types, many of which you have likely heard of before.

4 types of malware

Virus

A virus is malicious code designed to interfere with computer operations and cause damage to software and/or data. It is transmitted via a download where the malicious software is attached to a document or file that allows it to execute its code. It will lie dormant until run, where it will then hide itself within the target's file system and insert its own code to damage and/or destroy data on the system.

Worm

A worm is malware that self-replicates across computers and networks. Once a computer becomes infected by a worm, it will spread itself to other computers on that network. Unlike a virus, it does not need a host program to attach itself to in order to spread. It will infect devices through a downloaded file or through a network connection.

Ransomware

Ransomware is a type of malware that gains access to sensitive information within a system. Once it has gained access, it will encrypt the user's or organisation's sensitive data and demand payment to unlock it. When the payment is received, the attacker will unlock the data.

Spyware

Spyware is a type of malicious software that runs secretly and potentially sells information without consent. The goal isn't to disrupt or damage a system like a virus; the intent is to report sensitive information back to a remote user and can also grant remote access to the device. It's often used to steal financial or personal information.