The biggest backstabbing villain at "Big Brother" isn't Ariana Grande's brother, Frankie -- or any of the other contestants -- it's the CBS honchos who run the voting ... according to a new lawsuit.
A guy named Edwin Lyda claims he invented the system for text message voting and says he holds the patents to that system. He claims CBS jacked his invention and uses it each week on BB.
On the show, viewers vote in various ways -- by telephone, online, with a phone app or text messaging. The votes don't determine who stays or goes ... it's for things like who should win bonus prizes or who should get special perks in the house.
Lyda says his system for text voting is a big part of the show ... he wants a court to decide how much of BB's millions he's entitled to get ... then again, he could get nothing.
We called CBS for comment ... so far no word back.