A group of activists flew a drone over a key National Security Agency complex in Germany on Friday, dropping leaflets encouraging the intelligence workers inside to quit in protest over invasive surveillance.

The site of the drone fly-by, the Dagger Complex, is a U.S. military installation south of Frankfurt. It houses the European Cryptologic Center — a major source of signals and communications intelligence in Europe for the NSA. According to German media, its 1,100 employees monitor massive amounts of communications with tools such as XKEYSCORE, one of the programs revealed by NSA whistleblower Edward Snowden.

The group behind the drone mission, Intelexit, made headlines last week when it drove moving billboards past intelligence agencies in the U.S. and abroad. The billboards, framed by picturesque scenes of sunsets and American flags, include catchphrases such as “Complicit in mass surveillance and drone wars?” and “Listen to your heart, not to private phone calls,” directing observers to “exit intelligence.”

The latest campaign added a layer of symbolism with its use of a drone.

“We are inviting our many supporters to think of innovative ways to reach those who are in distress because of their role in supporting mass surveillance and drone warfare,” Sascha Fugel, a spokesperson for the campaign, said in a press release.

“Germany remains inactive and has to date taken no responsibility for the activities at the Dagger Complex,” Fugel continued. “We know that there are employees of the Dagger Complex who are experiencing great moral conflict because of their tacit involvement in spying.”

Activists who went to GCHQ headquarters, the British spying agency, were “really harassed by security/police who it seems, had already expected them,” Ariel Fischer, one of Intelexit’s organizers, wrote in an email to The Intercept. Freelance photographer Ben Grad accompanied a driver hired by Intelexit to drive around NSA headquarters in Fort Meade, Maryland. Grad told The Intercept that he and the driver took pictures on the NSA campus, but were told by security guards to delete them.

“In general, the response from the intelligence community so far has been to try and get rid of us as quickly as possible!” wrote Fischer.

Intelexit is supported by whistleblowers including Thomas Drake, a former senior NSA official who was indicted under the Espionage Act for sharing information about programs he viewed as expensive, illegal, and major risks to citizens’ privacy. Drake is featured in Intelexit’s homepage video.

According to a press release, Intelexit will be rolling out its networked support program for spies in its next phase.