Even as Russia’s cyber-attacks have received the bulk of recent attention, the Kremlin regime has ramped up other espionage activities.

In May, Frederico Carvalhão Gil, a senior member of Portugal’s Security Intelligence Service, was arrested for espionage. Accused of passing secrets to Russia, he was reportedly caught handing over materials pertaining to “NATO defense systems, the communication infrastructure between member countries and military bases.”

The United States and our NATO allies are in the crosshairs. Last year, NATO limited the size of non-member state delegations at its headquarters in Brussels. That decision affected only Russia and was driven by a desire to cut down on Russian intelligence officers’ operating inside NATO headquarters. Before the limit was imposed, Russia had two or three times as many delegates as any other non-NATO nation, and most of them were thought to be engaged in gathering intelligence.

U.S. allies in Europe face constant espionage from Russia. Estonia’s Internal Security Service last year reported that “the Federal Security Service (FSB), the Main Directorate of Military Intelligence of the General Staff and the Foreign Intelligence Service are all still active against Estonia.” Some of the activities are brazen. In 2014, the FSB kidnapped an Estonian Internal Security Service officer named Eston Kohver from inside Estonia and convicted him in a show trial before exchanging him a year later for an FSB spy arrested in 2012.

Lithuania’s intelligence agency warned in its 2015 annual report that Russia is working to infiltrate its armed forces and those of other NATO member states. The Czech Republic’s Security Information Service confirmed that Russia's is the most active foreign intelligence service operating inside the country. In the past few years, Russian spies have been caught in allied nations including Canada, the Czech Republic, France, Germany, and Poland.

Non-NATO allies have also been targeted. Swedish military facilities have been closely watched by Russian agents, and Swedish military personnel have been approached regularly by Russian intelligence agents. Sweden’s intelligence agency, Saepo, estimates that one-third of Russia’s diplomats in Stockholm are spies.

In the United States, the FBI busted a Russian spy ring operating in New York City just last year. The ring reportedly sought to recruit U.S. citizens as spies and stole economic intelligence. In 2010, Russia’s espionage activities briefly came to the forefront of the American public’s attention when the FBI broke up a 10-person Russian spy ring. Then FBI Assistant Director for Counterintelligence C. Frank Figliuzzi described the busted agents as Russia’s "cream of the crop."

In addition to espionage activities on U.S. soil, American diplomats abroad are regularly surveilled and harassed by Russian agents. An FSB guard beat up an American diplomat outside the U.S. embassy in Moscow this June.

NATO officials have also been targeted for harassment and threats. In one recent incident, a NATO officer at a Swedish restaurant was threatened by Russian agents who showed him pictures of his family while demanding information on alliance military exercises.

Putin’s aggressive use of espionage and intimidation of American diplomats abroad is merely one weapon in his push to compete against the West. Russia’s regime utilizes every available facet of power to advance its naked self-interest and undermine the United States, our allies, and the NATO alliance.

With the end of the Cold War the United States diverted intelligence resources away from Russia and greatly scaled back many of the area studies programs that helped analysts develop expertise on Russia. This trend only accelerated after the 9/11 attacks.

Today, Russian intelligence services are heavily focused on the United States, while Washington dedicates a far smaller percentage of its intelligence budget and assets on Russia. U.S. intelligence has been described by a senior American intelligence official as “playing catch-up big time” with Russia.

The next president must approach relations with Russia from a position of strength, seeing the regime clearly and implementing a comprehensive strategy for dealing with Russian aggression at home and abroad. The United States must work to counter Russian espionage and enact consequences for Russian harassment and aggression against U.S. diplomats overseas.

Espionage has once again emerged as an important tool in Russia’s geopolitical arsenal; it’s past time for the U.S. and our allies to recognize its importance as well.