The film, which follows three high school seniors as they attempt to impress their pals by throwing an outrageous party, was illegally downloaded a whopping 8.7 million times, according to a new report published by TorrentFreak.com.
The news comes as a surprise to industry buffs - the found-footage project solely features unknown actors and only grossed $100 million (GBP62.5 million) at the international box office.
Tom Cruise's Mission: Impossible - Ghost Protocol came in second, while The Dark Knight Rises was third.
Also making the top 10 list were The Avengers, 21 Jump Street, and The Dictator.
Last year's (11) prime target for Internet thieves was Fast Five.