Hollywood studios sue Megaupload
The lawsuit was filed in federal court in Alexandria, Virginia, seeking unspecified damages.
Megaupload and Dotcom already face criminal charges for copyright infringement, but Dotcom, a New Zealand resident, has been fighting extradition since his 2012 indictment.
Dotcom, who had his name changed from Kim Schmitz, has accused prosecutors of acquiescing to the Hollywood lobby and says he should not be held liable when people use his site to traffic in pirated entertainment.
Prosecutors and the studios say Megaupload was designed in a way to promote and reward users who trafficked in pirated works.
At its height, Megaupload accounted for an estimated 4% of all internet traffic.