Don’t install files from websites you don’t trust
Many of the spyware programs mask themselves as cute little programs such as toolbars, news bars, screen savers and so on. When you install these programs, you risk getting spyware and slowing down your computer. Because of this, you should only download the software from legitimate, reputable sources. Use websites such as https://www.consumerreports.org and follow their recommendations.
Protect your computer
Creators of spyware intentionally make them hard to remove. Spyware can 
also mess up your computer and your operating system. Rather than wait until you get spyware or viruses, protect your computer when it’s working as it is supposed to work. Many antiviruses offer real-time protection, including a free Microsoft Software Essentials suite that you can get for free. With most antiviruses, you can set a schedule as to when the antivirus will scan your software. You can set up an antivirus to do a full scan at night, when you are not using your device. This way, the protection software will be doing the work without you even noticing it and you will be safe. This also applies to Mac computers and MacOS.