Edward Snowden’s theft of files, whatever good it accomplished in igniting a national conversation on surveillance, also opened the door to more aggressive Russian intrusions in cyberspace. How could it not? According to the unanimous report of the House Permanent Select Committee on Intelligence, Snowden removed digital copies of 1.5 million files; 900,000 of them originated not with the NSA but Department of Defense documents, and concerned, among other things, the newly created joint Cyber Command. Other stolen files contained documents that originated with the British signal intelligence service, known as GCHQ, which Snowden had used his special access to obtain. One NSA file, a 31,000-page database, included requests to the NSA made by the 16 other agencies in the Intelligence Community for coverage of foreign targets. NSA Deputy Director Rick Ledgett, who headed the NSA’s damage assessment, described this database as the “keys to the kingdom” because it provided a roadmap to all of the gaps in coverage of Russia and other adversaries.

When sensitive compartmentalized information (SCI) is removed without authorization from the NSA’s secure facilities, as it was by Snowden, it is, by definition, compromised, regardless of what is done with it. Whether Snowden gave these files to journalists, Russians or Chinese intelligence, erased them or threw them in the Pacific Ocean, all the sources in them had to be considered compromised and shut down. So did the methods they revealed. The Pentagon, which did a more extensive damage assessment than the NSA, assigned hundreds of intelligence officers, in round-the-clock shifts, to go through each of the 1.5 million files to find all of the fatally compromised sources and methods in them. The self-destruct button then had to be pressed to close them down. Doing so punched a deep hole in the capabilities of the NSA, the Cyber Command, the British GCHQ, and other allied intelligence services—so deep that Booz Allen Vice-Chairman Michael McConnell, who had previously headed both the NSA and the office of National Intelligence, said, “An entire generation of intelligence was lost.” One measure of the seriousness of the ensuing blindness was the NSA’s failure to detect Russia’s preparations for the invasion of Ukraine in early 2014, according to the Wall Street Journal.

The damage was further deepened by Snowden’s defection to Russia. Putin revealed in a televised press conference on September 2, 2013, that Snowden had met in Hong Kong with what he called Russian “diplomats” before being offered sanctuary in Russia on June 11, 2013. Putin almost gloatingly prefaced the disclosure with the words, “I am going to tell you something I have never said before.” The chronology he then provided strongly suggested that Snowden met with the Russian “diplomats” before meeting with journalists from the Guardian between June 3 and 11. U.S. intelligence further determined, according to the House Permanent Select Intelligence Committee, that Snowden continued to be in contact with the Russian intelligence services after he arrived in Moscow and continued for three years. If so, he was in contact with officials of an adversary government both before and after he defected there. Fiona Hill, who served as an intelligence analyst on Russia for President Obama, told the editor of The New Yorker in 2017, “The Russians, partly because they ‘have’ Edward Snowden in Moscow,’’ possess “a good idea of what the U.S. is capable of knowing. They got all of his information. You can be damn well sure that [Snowden’s] information is theirs.” If so, all the sources and methods in his head were also compromised.

The adage when the cat is away, the mice will play certainly applies to the highly opportunistic game of intelligence. If one side loses the sources and methods that allow it to check an adversary, that adversary gains leeway to mount covert operations.

The diminished capacity of the U.S. that proceeded from Snowden’s theft might well have encouraged the Russians to engage in covert operations. What Barack Obama correctly called the “disclosure” operations, including those preceding the 2016 election, may be only the tip of a much bigger and more submerged iceberg.

The good news is that intelligence is not a static enterprise. The NSA will in time, if it has not done so already, remedy the damage by replacing the lost generation of sources and methods with new ones. But until it, Putin can be expected to continue to use the impaired capacity of the NSA to his advantage.