The National Security Agency has lost hundreds of its most talented employees over the past few years in a major exodus that some say could undermine national security, The Washington Post reports. The spy agency has not disclosed the number of personnel who’ve left, but current and former U.S. officials cited in the report say hundreds of hackers, engineers, and data scientists have left since 2015 for work in the private sector, a move largely attributed to low morale. The departments hit the hardest were reportedly those responsible for collecting and analyzing the intelligence that goes into the president’s daily briefing, as well as monitoring threats to national security, including ISIS, Russia, and North Korea. The “NSA is at this moment experiencing stress that is constant and unrelenting,” one former senior intelligence official told the Post. Former employees cited in the report blamed a controversial reorganization within the agency and an atmosphere of suspicion in the wake of several breaches.