A deceptive pattern is a way of presenting choices to people that are manipulative, tricking them into making choices that are not in their best interest.
The term is often applied in the field of user experience design, and cookie banners are a perfect example of deceptive patterns.
Not only are cookie banners themselves often superfluous – purely functional cookies usually do not require them, only advertising/tracking cookies do.
But more often than not, the “accept all cookies” choice is presented larger, or in green, giving it all the trappings of the obvious choice to make, when users should likely prefer the choice that minimized the data being collected about them.
Deceptive patterns and informed consent have an interesting relationship, as deceptive patterns often do provide the required information for requesting consent, while simultaneously manipulating the user’s choice.
Note that deceptive patterns used to be called “dark patterns”, and you may still find this term in use. It’s better to speak about deceptive patterns or deceptive design, though, because the association between “dark” and “bad” reinforces racist stereotypes.