The Terror Question No Signs of Deliberate Attack in Blackout, But Possibility Not Ruled Out Aug. 15— Despite official assurances to the contrary, could terrorists have exploited a vulnerable power grid to cause Thursday's massive blackout? The cause of the failure remains a mystery, as power was gradually returning from the largest-ever blackout in the nation's history, affecting some 50 million people in areas from Michigan to New York. And while there is no indication the power grid was sabotaged, some experts caution it is too soon to rule out any possible explanation — including cyber-terror. "Anybody who says that...