When Alexander Bortnikov, the head of Russia’s internal security service, told me during an early August 2016 phone call that Russia wasn’t interfering in our presidential election, I knew he was lying. Over the previous several years I had grown weary of Mr. Bortnikov’s denials of Russia’s perfidy — about its mistreatment of American diplomats and citizens in Moscow, its repeated failure to adhere to cease-fire agreements in Syria and its paramilitary intervention in eastern Ukraine, to name just a few issues.

When I warned Mr. Bortnikov that Russian interference in our election was intolerable and would roil United States-Russia relations for many years, he denied Russian involvement in any election, in America or elsewhere, with a feigned sincerity that I had heard many times before. President Vladimir Putin of Russia reiterated those denials numerous times over the past two years, often to Donald Trump’s seeming approval.

Russian denials are, in a word, hogwash.

Before, during and after its now infamous meddling in our last presidential election, Russia practiced the art of shaping political events abroad through its well-honed active measures program, which employs an array of technical capabilities, information operations and old-fashioned human intelligence spycraft. Electoral politics in Western democracies present an especially inviting target, as a variety of politicians, political parties, media outlets, think tanks and influencers are readily manipulated, wittingly and unwittingly, or even bought outright by Russian intelligence operatives. The very freedoms and liberties that liberal Western democracies cherish and that autocracies fear have been exploited by Russian intelligence services not only to collect sensitive information but also to distribute propaganda and disinformation, increasingly via the growing number of social media platforms.

Having worked closely with the F.B.I. over many years on counterintelligence investigations, I was well aware of Russia’s ability to work surreptitiously within the United States, cultivating relationships with individuals who wield actual or potential power. Like Mr. Bortnikov, these Russian operatives and agents are well trained in the art of deception. They troll political, business and cultural waters in search of gullible or unprincipled individuals who become pliant in the hands of their Russian puppet masters. Too often, those puppets are found.