And how to avoid it.

What is Malware?

Malware is separated into three main categories, viruses, Trojan horses, Spyware.
Viruses - a viruses is software that does harm to your computer, it copies its self but needs contact to spread (connecting to another computer, internet, etc.).

Trojan Horses - A Trojan Horse is software that seems legit but allows someone else to access your computer. For instance, you see a free game on the web and you install it, if it is a Trojan Horse you have just gave access to someone else to your computer.

Spyware - Spyware is software that obtains personal information such as credit card info or contacts. It can also record keystrokes so if you buy something online it can get your credit card information.

How to avoid - Some of the ways to avoid this is to get legit antivirus software (antivirus software from a company that you trust), make sure your firewall is turned on so your computer will block untrusted connections which can do damage but most of all, common sense - be aware of what your doing on the internet and what sites you are going to.