Unwanted Programs

Potentially unwanted programs (PUPs) include adware, browser parasites, spyware, and other applications that install themselves on a computer — such as rogue security software, toolbars, and PC diagnostic tools — typically without the user's informed consent. They are increasingly found on social network and user-generated content sites where users are fooled into downloading them, and once installed are usually exceedingly difficult to remove.

Adware is typically used to call for pop-up ads to display when the user visits certain sites. While annoying, adware is not typically used for criminal activities. A browser parasite is a program that can monitor and change the settings of a user's browser, such as changing the home page or sending information about visited sites to a remote computer. Browser parasites are often a component of adware.

A well-known adware case is Superfish: Lenovo shipped laptops with Superfish preinstalled, which injected shopping results into the browser and created a security risk by enabling others on the same Wi-Fi network to silently hijack the browser and collect anything typed into it.

Spyware can be used to obtain information such as a user's keystrokes, copies of e-mail and instant messages, and even take screenshots — thereby capturing passwords or other confidential data. Spyware is more dangerous than adware because it directly captures sensitive information, making it a serious threat to e-commerce users.