Portuguese intelligence officers have decided to search for other moles after they discovered one of their own passed NATO secrets to Russia.

Italian police arrested Frederico Carvalhão, a senior officer in Portugal’s SIS intelligence service, along with an alleged Russian SVR intelligence agent. However, SIS believe others helped Carvalhão extract confidential and sensitive information.

The Telegraph reports:

Augusto Santos Silva, the Portuguese foreign minister, confirmed on Wednesday that there was “an ongoing judicial investigation” into the case. The focus is believed to be on discovering who helped Mr Carvalhão extract top-secret documents from Ameixoeira Fort, the SIS headquarters in Lisbon.

The use of USB sticks is prohibited inside Ameixoeira, access to all printed documents is registered and those classified as secret have an invisible watermark to allow for the detection of anyone who has removed them. Yet Mr Carvalhão was allegedly caught while handing over six “top secret” documents covering Nato defence systems, the communication infrastructure between member countries and military bases.

Carvalhão allegedly traveled all over the European Union since 2014 to meet with his Russian contact. Officials also feel he kept relationships with numerous women in the countries.

Interestingly enough, the Russians used an “illegal” for the handler, “meaning he was operating without any official protection.” In espionage games, the receiving countries usually use people posing as diplomats as handlers since they receive diplomatic immunity. This shows that the Kremlin considered Carvalhão an important asset:

The identity of the SVR officer in custody has not been released by Italian authorities, but Illegals are an elite cadre in Russian intelligence circles, much less frequently encountered than their counterparts posing as diplomats. They are also much tougher to detect, since they aren’t working at any embassy or consulate, and last year’s FBI arrest of an SVR Illegal in New York City—where he was spying on Wall Street—was a coup for American counterintelligence.

Officials discovered “[D]ocuments and an unspecified quantity of cash” at Carvalhão’s home. They think he charged the Russians €10,000 ($11,179.70) for each document he gave them.

The news comes as a big blow to the international community since Eastern Europe countries have asked for a larger NATO presence to deter possible Russian invasions. In 2015, the Swedish intelligence service discovered that the Russian embassy houses more spies than actual diplomats:

“Of the Russian embassy’s diplomatic staff, about one-third of them are not actually diplomats, they are in fact intelligence officers,” Wilhelm Unge, Saepo’s chief counter-espionage analyst, told reporters as the agency presented its annual security report.

“This is a very constant number, this is the way things look year after year,” he said.

For the past few years, Sweden has moved closer to NATO even though Russian officials have threatened the country if anything becomes permanent. Despite the threats, on Thursday, the Swedish parliament ratified an accord to allow NATO access in the country even though they do not belong to the organization.

[Featured image via Wikimedia Commons]