“Anyone have a Spectrum user ID & password I can trade for?” one Twitter user wrote last month. Another thanked her friend “for giving me his Spectrum username and password to watch the World Series Game 7.” A third tweeted: “Totally figured out my parents Spectrum password and can watch cable now through my Apple TV. I literally love my life.”

Tom Rutledge has had enough. The chief executive officer of Charter CommunicationsInc., which sells cable TV under the Spectrum name, is leading an industrywide effort to crack down on password sharing. It’s a growing problem that could cost pay-TV companies millions of subscribers—and billions of dollars in revenue—when they can least afford it.

“There’s lots of extra streams, there’s lots of extra passwords, there’s lots of people who could get free service,” Rutledge said at an industry conference this month. The CEO has said that one unidentified channel owner had 30,000 simultaneous streams from a single account.