This is going to blow your mind -- but the people who wrote "Down Under" ripped off the melody in their 80s hit from the classic campfire song, "Kookaburra" ... this according to a new court ruling.



An Australian judge just ruled that "Men at Work" owe a Fosters-size can of royalties to the music company who owns the rights to the 70-year-old song.

If you've ever been to summer camp -- it's all starting to come together now.

So far the band isn't talking.

"You better run ... you better take cover."