Last week, Austria expelled three Russian diplomats accused of using diplomatic cover for espionage activities in Vienna.

Soon after, Foreign Minister Beate Meinl-Reisinger said that Austria was taking a tougher approach to spying activities, calling it a “security issue” for the country.

“We have communicated this clearly and unequivocally to the Russian side, including regarding the ‘antenna forest’ at the Russian representation,” she said in a statement. “It is clear that it is unacceptable for diplomatic immunity to be used to conduct espionage.”

What was she referring to?

Researchers and journalists have warned that several Russian diplomatic buildings in Vienna are fitted with large antenna systems and satellite dishes that could be used to intercept communications.

It’s not unusual for embassies to use rooftop antennas and satellite systems to maintain secure communications with their governments.

Under Article 27 of the Vienna Convention on Diplomatic Relations, diplomatic missions may use secure means of communication. However, an embassy is only allowed to install or operate a wireless radio transmitter with the consent of the receiving state.

However, an investigation published in March by the Financial Times, which cited officials and analysts monitoring the sites, reported that the satellite dishes appeared to move and reposition frequently, a behaviour that analysts said is unusual for systems used solely for diplomatic communication.

Erich Möchel is an Austrian investigative journalist who has monitored satellite dishes and antenna systems on Russian diplomatic buildings in Vienna alongside a group of senior Austrian technologists and electronics engineers who call themselves Nomen Nescio.

He told EU News’ fact-checking team, The Cube, that one antenna system on Russia’s embassy buildings in Vienna’s third district “points far to the west”, which he said was “not usual embassy communication.”

The antenna points toward commercial satellites carrying communications traffic between Europe and Africa, rather than toward satellites that are associated with communicating with Moscow.

According to Möchel, one Russian diplomatic building in Vienna’s 22nd district appears to function as a “pure signals intelligence station” with several dishes pointing towards satellites that carry communications traffic between Europe and Africa.

Nomen Nescio has observed that one dish is regularly repositioned and then returned to its normal orientation. This dish appears to be “used for searching,” according to Möchel.

“Possibly, they are looking for something, some special channel on another satellite,” he said.

Nomen Nescio also identified unusual rooftop structures made from lightweight materials such as wood and plastic. Möchel said these structures resembled radomes, weatherproof enclosures designed to protect antennas and obscure their direction.

Diplomatic rooftops under scrutiny

Allegations surrounding rooftop surveillance systems on diplomatic buildings are not new.

Reporting by Der Spiegel, based on documents leaked by exiled former NSA Edward Snowden, alleged that the US embassy in Berlin housed rooftop surveillance equipment used for signals intelligence collection.

In 2013, Germany’s foreign ministry invited the British ambassador to a meeting amidst allegations that British intelligence had established a “covert listening post” on top of the embassy’s roof to eavesdrop.

Russia is no stranger to similar allegations. A 2023 investigation by Central European media outlet VSquare reported that specialised equipment on embassy roofs from Warsaw to Brussels had the capacity to intercept electronic communications of the countries it was based in, according to multiple former intelligence officials interviewed by the outlet.

Sergei Jirnov, a former KGB officer, told The Cube that antennas on diplomatic buildings could serve “two purposes: communications with Moscow and espionage activities in the host country.”

Claude Moniquet, former agent for France’s foreign intelligence agency DGSE, told us that some diplomatic antennas could theoretically be used for “the interception of radio waves, microwave links, satellite communications, unencrypted internet traffic, and the collection of mobile identifiers and metadata through IMSI-catcher-type devices.”

He added that Chinese and Russian services use similar methods, and described Brussels, Vienna and Geneva as major hubs for such activity, given that they host international bodies.

Vienna in particular has long been associated with espionage due to the presence of the United Nations, the International Atomic Energy Agency, the Organisation for Security and Co-operation in Europe and the Organisation of the Petroleum Exporting Countries.

Austria has expelled fewer Russian diplomats since Moscow’s full-scale invasion of Ukraine in 2022, compared to countries such as Germany, Poland and France.