(also potentially unwanted program, PUA)
An unwanted application that installs itself alongside another type of software. It is not necessarily destructive — some of these unwanted applications only annoy users with inconveniences like pop-up ads, using up a device’s resources, or changing the default browser. But PUAs can also include spyware, adware, and other forms of malware.
Adware. Malicious software that shows users ads by popping them up on their screen at random times or redirecting them to ad-ridden websites.
Spyware. Hidden malicious software that monitors users’ activities on the device and logs their keystrokes to steal personal data, like login credentials and banking information.
Browser hijacker. Malicious software that takes over the user’s browser and showers them with ads, changes the search engine and homepage, or redirects them to random websites.