The dispute between Twitter and the U.S. intelligence industry that broke into public view this week actually began as long ago as last fall, sources familiar with the matter tell CNBC.

The Wall Street Journal reported this week that Twitter has cut off U.S. intelligence agencies from a service that sifts through the entire output of Twitter's social media postings. That comes as Silicon Valley and the U.S. government have been engaged in a heated dispute over the degree to which American tech companies should cooperate with U.S. law enforcement and intelligence agencies, such as the FBI and CIA.