A Potentially Unwanted Program (PUP) is software that a user may perceive as unwanted or unnecessary. It is used as a subjective tagging criterion by security and parental control products. Such software may use an implementation that can compromise privacy or weaken the computer’s security. Companies often bundle a wanted program download with a wrapper application and may offer to install an unwanted application, and in some cases without providing a clear opt-out method.

Antivirus companies define the software bundled as potentially unwanted programs which can include software that displays intrusive advertising (adware), or tracks the user’s Internet usage to sell information to advertisers (spyware), injects its own advertising into web pages that a user looks at, or uses premium SMS services to rack up charges for the user. A growing number of open-source software projects have expressed dismay at third-party websites wrapping their downloads with unwanted bundles, without the project’s knowledge or consent.