Macs are incredibly secure, but malware does exist. It generally gets installed through social engineering (tricking a user to install a plug in or browser extension), and it's still extremely annoying to deal with. Mac malware can often be cleaned manually, but I recommend Malwarebytes. A lot of you may remember The Sweet Setup's tip on removing InstallMac, the program recommended there (AdwareMedic) is now called Malwarebytes. If you ever find yourself in a situation where your Mac has malware, be sure to run this app to clean it up automatically.

Download Malwarebytes for free (personal use only).