"U.S. EPA had an unwanted visitor almost five years ago.
On Nov. 1, 2011, investigators began looking into someone gaining access to the local area network — the physical, interconnected system of computers, servers and other devices — in EPA's Washington, D.C., headquarters on Pennsylvania Avenue. The trespasser had gained access with a personal computer to the agency's network at least six times, specifically the east and north buildings of the complex.
How serious was the breach?
'The impact of this incident represents a compromise of the command and control of EPA systems and the EPA network,' the agency's inspector general said in an investigative report."