Russian intelligence operatives at the beginning of every year order copies of publicly available directories that include the names, job descriptions, and contact information of U.S. federal government and congressional employees in order “to gather intelligence on the persons and institutions” in the West, according to Yahoo, citing a Estonian foreign intelligence service report on Tuesday.

The congressional phonebooks, bought from U.S. Leadership Connect and a local periodical provider, illustrate how Moscow uses open source intelligence to gather as much information as possible on potential American targets for either surveillance or potential recruitment.

“The Russians have always taken advantage of the relative openness of societies in the West,” former CIA officer Robert Dannenberg told Yahoo.

He added that Moscow uses it “mostly for targeting purposes but also to fill holes in collection,” emphasizing that in the 2016 American presidential elections the open source data allowed Russians to target specific audiences for “active measures.”

Thomas Rid, a professor of strategic studies at the Johns Hopkins School of Advanced International Studies, agreed that this Russian technique is not new. “There’s a long track record of Soviet intelligence using publicly available records, but not easily available, for espionage and active measures,” he told Yahoo.

The new report by Estonia’s intelligence, considered as one of the world’s top experts on Russian espionage, details Moscow’s ongoing ambitions regarding its military, overseas meddling and foreign relationships.

The report includes a section on how the Russian foreign intelligence agency, the FSB, targets people using human, cyber and signals intelligence.

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