Malwarebytes Anti-Malware for Mac
is free tool that allows you to scan your Mac for malware and adware to keep you safe. It's fast to download and set up, and once done you will be able to easily scan your computer for any security issues related to malware and adware. After the scan is completed, you can quickly select what to remove. Although it is a good program to catch unwanted malware and adware, it does not check for changes to your desktop settings or other programs that might have been installed maliciously.
Malwarebytes Anti-Malware for Mac is also available on Windows