Thinking about malware files usually leads to thoughts of some criminal organization looking to attack you and steal your files, money or personal data for their own benefit. While attacks through resident malware can often be attributed to criminals, there are dangers to privacy looming from a completely different corner - potentially unwanted applications (PUAs).
These stealthy applications are often installed on a device by hitching a ride with downloads of useful software. After they sneak onto your computer, they usually hijack your browser, insert advertisements, and track you while you surf the Internet. If this doesn't seem like a big deal, think again - these apps could be analyzing and running even on secure sites (like your bank portal, ecommerce/credit card processing website, or email infrastructure), sending data back to their servers.
Although analyzing and categorizing potentially unwanted software is a complex problem, there are general rules that some security vendors follow to classify PUAs. For example, Malwarebytes follows these specific criteria:
Article Link: https://blog.reversinglabs.com/blog/sneaky-tools-infiltrating-your-mac-fortress