Stealing secrets from adversaries, let alone allies, had always been limited by daunting logistics and the risk of what intelligence professionals call “blowback,” the costs associated with being discovered, whether by allies or enemies. Those Cold War constraints seemed to crumble in the Internet age.

Now that equilibrium is being scrambled again as U.S. spy agencies confront cascading disclosures of their secrets on a magnitude they never envisioned, triggered by a former intelligence contractor, Edward Snowden. This presents a new quandary for the United States: Curtail spying on allies and lose critical intelligence. Or continue the programs and take on serious diplomatic risks if discovered.

The disorientating effect of Snowden’s revelations was evident as U.S. officials sought to contain the fallout during congressional testimony this week.

“The conduct of intelligence is premised on the notion that we can do it secretly, and we don’t count on it being revealed in the newspaper,” Director of National Intelligence James R. Clapper Jr., said, essentially acknowledging that a leak of Snowden’s scale was never factored into U.S. spy agencies’ cost-benefit analysis.