The White House says it has foiled an attempt to infiltrate its computer system.
White House spokesman Jay Carney said the attack had been identified and isolated. He said there was no indication that any data had been removed.
Carney described the attack as "spear-phishing" and said such efforts against government computer systems are "not infrequent."
"Phishing" is a tactic that involves sending an e-mail that falsely claims to be from a legitimate enterprise in an attempt to trick the user into turning over information.
Last year, Google blamed computer hackers in China for a phishing effort against Gmail accounts of several hundred people, including senior U.S. government officials and military personnel.
Based on reporting by AP and dpa