A computer hacker stole a file containing the names and Social Security numbers of 1,500 people working for the Energy Department's nuclear weapons agency. Officials told a congressional hearing Friday that the department's senior managers were informed only two days ago of last September's incident, which was somewhat similar to recent problems at the Veterans Affairs Department. None of the victims was notified, they said. The data theft occurred in a computer system at a service center belonging to the National Nuclear Security Administration in New Mexico. The file contained information about contract workers throughout the agency's nuclear weapons complex, a department spokesman said.