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National Security Agency workers in Utah found themselves under an eye in the sky Friday morning — an airship emblazoned with "Illegal Spying Below," floating directly above the agency's huge data center outside Bluffdale.

The airship (technically, blimps have no rigid structure) was a stunt engineered by Greenpeace, the Electronic Frontier Foundation and the Tenth Amendment Center to promote a new website, StandAgainstSpying.org, that lets people track legislators' voting records on NSA surveillance matters.

Why Greenpeace? For one thing, they're part of an ongoing lawsuit against the NSA concerning alleged First Amendment violations by the agency. "We can't have clean air and clean water if we don't have a healthy democracy with basic human freedoms," explained Greenpeace's David Pomerantz in an email to NBC News. "Freedom of association, speech and privacy are crucial for our democracy."

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The NSA declined to comment on the airship directly, but added in an emailed statement to NBC News that "All of NSA's operations are conducted in strict accordance with the rule of law."

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Social

Protestors Launch A 135-Foot Blimp Over the NSA’s Utah Data Center http://t.co/e5vYoPOk7R — Andy Greenberg (@a_greenberg) June 27, 2014

(AWESOME!) Group flies blimp over Utah NSA data center to protest 'illegal mass surveillance program' http://t.co/iMPgo84aU1 — Genghis Don (@donbcivil) June 27, 2014

It's true. EFF and @Greenpeace flew a 135 ft. airship over the NSA data center in Utah. https://t.co/7HQuXZDjpk pic.twitter.com/jtouh3YNmd — EFF (@EFF) June 27, 2014

— Devin Coldewey, NBC News