Deception is a malicious functionality that makes the program dishonest or conceals trickery. Here are examples of such malicious functionalities. Cases of deception that involve taking people's money are listed in Proprietary Fraud.

• 2022-02

  Honorlock set a network of fake test answer honeypot sites, tempting people to get exam answers, but that is a way to entrap students, so as to identify them and punish them, using nonfree JS code to identify them.

• 2020-11

  HP tricked users into installing a mischievous update in their printers that made the devices reject all third-party ink cartridges.

• 2020-02

  Many Android apps fool their users by asking them to decide what permissions to give the program, and then bypassing these permissions.

  The Android system is supposed to prevent data leaks by running apps in isolated sandboxes, but developers have found ways to access the data by other means, and there is nothing the user can do to stop them from doing so, since both the system and the apps are nonfree.

• 2019-04

  Volkswagen programmed its car engine computers to detect the Environmental Protection Agency's emission tests, and run dirty the rest of the time. In real driving, the cars exceeded emissions standards by a factor of up to 35.

  Using free software would not have stopped Volkswagen from programming it this way, but would have made it harder to conceal, and given the users the possibility of correcting the deception.

  Former executives of Volkswagen are being sued over this fraud.

• 2019-03

  OfficeMax cheated customers by using proprietary “PC Health Check” software rigged to give false results, deceiving the customer into thinking per computer was infected and buy unneeded support services from the company.

• 2019-02

  Twenty nine “beauty camera” apps that used to be on Google Play had one or more malicious functionalities, such as stealing users' photos instead of “beautifying” them, pushing unwanted and often malicious ads on users, and redirecting them to phishing sites that stole their credentials. Furthermore, the user interface of most of them was designed to make uninstallation difficult.

  Users should of course uninstall these dangerous apps if they haven't yet, but they should also stay away from nonfree apps in general. All nonfree apps carry a potential risk because there is no easy way of knowing what they really do.

• 2016-11

  Audi's proprietary software used a simple method to cheat on emissions tests: to activate a special low-emission gearshifting mode until the first time the car made a turn.

• 2016-09

  Many proprietary programs secretly install other proprietary programs that the users don't want.

• 2016-07

  The proprietor of the Pokémon Go game invites restaurants and other businesses to pay to have the game lure people there.

• 2015-11

  A top-ranking proprietary Instagram client promising to tell users who's been watching their pictures was in reality stealing their credentials, advertising itself on their feed, and posting images without their consent.