|WASHINGTON (CNN) -- The FBI and the Pentagon are investigating whether Chinese spies have been hacking into U.S. government computer systems, U.S. officials said Thursday.
Officials are trying to determine whether the continuing hacking efforts are sponsored by Beijing or merely involve hackers using Chinese Web sites to mask their origins, they said.
In recent years units in the FBI Cyber-crime Division, established to combat computer intrusions, have seen hundreds of cases in which hackers using Chinese Web sites have compromised unclassified official U.S. networks.
One U.S. government official, who asked not to be identified, said government investigators had been involved for several years in "working this problem."
"You can't just jump on a plane and go to China and start questioning people," another government official said.
The FBI declined to comment because of the sensitive nature of the investigations.
Government officials acknowledge many of the attacked Web sites have been unclassified Defense Department sites.
Several other agencies involved with national security, including the departments of Energy and Homeland Security, also have been targeted, the officials said.
The investigation into the hacking and the debate about the origin were first reported by Federal Computer Week and The Washington Post.
These Chinese all the day playing online games makes them ultra hackers.