Far more civilians have been killed by U.S. drone strikes in Pakistan's tribal areas than U.S. counter-terrorism officials have acknowledged, a new study by human rights researchers at Stanford University and New York University contends. The report, Living Under Drones," also concludes that the classified CIA program has ... turned the Pakistani public against U.S. policy in the volatile region. "Real people are suffering real harm" but are largely ignored in government or news media discussions of drone attacks, said James Cavallaro of Stanford, one of the study's authors. Cavallaro said the study was intended to challenge official accounts of the drones as precise instruments of high-tech warfare with few adverse consequences. The study concludes that only about 2% of drone casualties are top militant leaders. The study authors did not estimate overall civilian casualties because of limited data, Cavallaro said. But it cites estimates by the Bureau of Investigative Journalism, which has reported extensively on drone strikes, of 474 to 884 civilian deaths since 2004, including 176 children. In April, Obama's top counter-terrorism advisor, John Brennan, described civilian casualties from drone strikes as "exceedingly rare." The study challenges official versions of three attacks between 2009 and 2011, including a drone strike on March 17, 2011, that killed an estimated 42 people.