The 56-year-old Belgian, whose work is often classified, did not consider himself naive. But he took the news personally, and more so when he heard unofficial explanations from Washington.
" 'Everybody knows. Everybody does' — Keith Alexander said that," de Kerchove said in an interview. "I don't like the idea that the NSA will put bugs in my office. No. I don't like it. No. Between allies? No. I'm surprised that people find that noble."
Comparable reactions, expressed less politely in private, accompanied revelations that the NSA had tapped the cellphones of German Chancellor Angela Merkel and President Dilma Rousseff of Brazil. The blowback roiled relations with both allies, among others. Rousseff canceled a state dinner with Obama in September.
When it comes to spying on allies, by Snowden's lights, the news is not always about the target.
"It's the deception of the government that's revealed," Snowden said, noting that the Obama administration offered false public assurances following the initial reports about NSA surveillance in Germany "The U.S. government said: 'We follow German laws in Germany. We never target German citizens.' And then the story comes out and it's: 'What are you talking about? You're spying on the chancellor.' You just lied to the entire country, in front of Congress."
In private, U.S. intelligence officials still maintain that spying among friends is routine for all concerned, but they are giving greater weight to the risk of getting caught.
"There are many things we do in intelligence that, if revealed, would have the potential for all kinds of blowback," Clapper told a House panel in October.
U.S. officials say it is obvious that Snowden's disclosures will do grave harm to intelligence gathering, exposing methods that adversaries will learn to avoid.