Nearly a quarter of the group’s recommendations judged to have been “fully implemented” had lost that status. Much of the damage has occurred at the Cybersecurity and Infrastructure Security Agency, responsible for coordinating defense of the nation’s civilian networks. Launched in 2018, the agency has generally won plaudits for helping secure election systems around the country, providing early warning of attacks, and helping companies and infrastructure managers bolster their cyberdefenses. Since January, the agency has lost nearly a third of its personnel — including most of its senior staff — to layoffs, buyouts and early resignations. Threats to the nation’s digital networks are not going to shrink.