Twitter has reportedly barred U.S. intelligence agencies from accessing analytics service Dataminr, which is used to identify unfolding events such as terror attacks and political unrest, The Wall Street Journal reported Sunday. The ban has not been publicly announced, but was confirmed to the Journal by a senior U.S. intelligence official and other people familiar with the matter. Twitter owns about a 5 percent in Dataminr, which is the only company it allows to access its entire real-time stream of public tweets and sell it to clients. Twitter reportedly appeared to be concerned about the “optics” of looking too close to American intelligence services, the senior official told the Journal. The company claims it first notified clients about the Brussels attacks 10 minutes before news outlets, and also gave the American intelligence community an alert about the Paris attacks shortly after they began to unfold in November.