The letter from full committee Chairman John Dingell, D-Mich., ranking Republican Joe Barton of Texas and three subcommittee leaders notes that cyber-security weakness at Energy could allow "individuals or groups backed by nation-states" to access classified information.
The department issued a report with new cyber-security rules after a 2005 attack removed detailed personnel information on 1,500 employees of the National Nuclear Security Administration. In an incident last year, hundreds of classified documents from the Los Alamos National Laboratory were found in a worker's home during a drug raid.
The lawmakers note that a year later, "it's unclear whether [the department's] revitalization program is working." They want a GAO report on the security of Energy networks and the success of security improvements.