NIPRNET is the usual way to refer to what was originally the U.S. military's Non-Classified Internet Protocol Router Network, but is now officially the Unclassified but Sensitive Internet Protocol Router Network. It is not authorized for the transfer of classified information, but access to it is restricted to U.S. military personnel, civilian government employees, and military contractors. To varying extents, it can be reached, with suitable logins to gateways, from the public Internet.
NIPRNET, along with SIPRNET at the SECRET classification level and JWICS at the TOP SECRET and compartmented control system levels, is an overlay — some might call it a virtual private network — on the Defense Information Systems Network.
There is no such thing as a MIPRNET computer or terminal. NIPRNET is a network, and its users typically connect their computers to a local area network, which, through one or more routers and appropriate security equipment, connnect the worldwide NIPRNET. User organizations thus need to control access to local area networks that are actively part of NIPRNET. A military reserve training organization at a university might have the LAN in its building connect to NIPRNET, and even reach the rest of the NIPRNET by tunneling through the general university network, but there can be no mixing between that general network and the NIPRNET LAN. Wireless LANs (WLAN) must be restricted and range, and have approved security connectivity to NIPRNET.
Four Department of Defense agencies have joint responsibility for SIPRNET: