The alert was issued after officials said a posting on a "jihadist" website had called for a cyber attack on U.S. financial websites during the month of December in retaliation for Muslims being held at the U.S. Guantanamo Bay detention center for terrorism suspects.
A spokesman for the U.S. Department of Homeland Security said there was no evidence of an immediate danger to computer networks.
Meanwhile, in Los Angeles, a Romanian man has been indicted on charges of hacking into more than 150 U.S. government computers, causing disruptions that cost NASA, the Energy Department, and the Navy nearly $1.5 million.
Twenty-six-year-old Victor Faur faces up to 54 years in prison if convicted on all counts.
After hacking into and taking control of the computers, Faur programmed the machines to operate as chat rooms so he could communicate with other hackers.
(AP, Reuters, BBC)
