An malicious software

Trojan Horse, Viruses, Spyware

Trojan Horse: A trojan horse is something that seems legit but allows a virus or someone else to access you computer.

Viruses: A virus copies itself. Once it's in your computer it sends it's self to other people/devices usually through email and that's how it spreads.

Spyware: Spyware secretly secures your personal information

How do you avoid it?

You can avoid all of these viruses by getting AntiVirus software. AntiVirus software is used to detect and get rid of viruses that can hurt your computer. Another good back up is a firewall. A firewall is pretty much a filter in your computer, meaning anything you download is picked apart to make sure it won't harm your computer.