Ms. Manfra, who joined Homeland Security in 2007, witnessed and participated in many of the department’s efforts to carve out a space for itself alongside the Defense Department as a center of cybersecurity-focused, technically literate activity in the federal government. Her successor will be largely responsible for determining whether D.H.S. continues to grow in its credibility as a cybersecurity organization both within the government and outside it, or instead loses much of the ground it has made up in trying to become an equal partner to the Defense Department’s cybersecurity expertise and authority.

Just as Homeland Security was working on strengthening its cybersecurity work force for the past several years, so, too, was the White House. After hackers linked to the Russian government breached unclassified White House networks in 2014, Mr. Obama established a team within the White House focused on securing the Presidential Information Technology Community network. This was the team that Mr. Vastakis worked on, until it was absorbed by the Office of the Chief Information Officer in July. “This is a significant shift in the priorities of senior leadership, where business operations and quality of service take precedence over securing the president’s network,” Mr. Vastakis wrote of the reorganization in his October memo.

The fact that the White House is emphasizing convenience of communications at the expense of security is not entirely surprising in light of recent reports on President Trump’s continued use of unsecured phone lines and personal electronic devices. But even so, the disregard for security staff members described in Mr. Vastakis’s memo is alarming and extreme. It suggests that people who care about the security of White House data and networks are no longer welcome in the executive office of the president, at the same time that people who care about foreign interference in American elections are in increasingly short supply in the federal government. These will not be easy positions to fill — not just because cybersecurity professionals are in short supply and high demand, but also because the message being conveyed by this administration is that cybersecurity is no longer a priority for the federal government, especially civilian efforts focused on the defense of critical infrastructure and government facilities.

There have been warning signs of this shift even before this year. In May 2018, the White House eliminated the cybersecurity coordinator position on the National Security Council, suggesting that it might no longer be as focused on internet-based threats. But the impact of that decision pales in comparison to the mass departures of cybersecurity staff in 2019.

Mr. Vastakis concluded his memo with a grim warning: “I foresee the White House is posturing itself to be electronically compromised once again. Allowing for a large portion of institutional knowledge to concurrently walk right out the front door seems contrary to the best interests of the mission and the organization as a whole.” As we head into 2020, worrying about the integrity of our elections, the growing scourge of ransomware and the increasingly sophisticated forms of cyberespionage and cybersabotage being developed by our adversaries, it’s disconcerting to feel that many of our government’s best cybersecurity minds are walking out the front door and leaving behind too few people to monitor what’s coming in our back doors.

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