The Pentagon has granted many exceptions, possibly numbering in the thousands, to allow staff members who administer secure computer networks to use flash drives and other portable storage devices, department spokesmen say. The exceptions to policies barring the use of such devices could make it easier for rogue employees to remove sensitive documents. But officials say waivers go to people who update software and run helpdesk services for the Pentagon's vast computer network and are needed to run the system efficiently. The U.S. government's handling of sensitive documents has come under scrutiny since Edward Snowden, a systems administrator for a contractor with the National Security Administration, copied classified materials at a Hawaii installation and leaked them to the news media. Snowden used a simple flash drive to store the materials, according to a government source close to the investigation. Storage devices have been a concern at the Defense Department sinc