According to Department of Homeland Security spokesman Russ Knocke, a threat to target the banking industry was seen on an Islamic extremist website.
However, Mr Knocke also conceded that there was no other evidence to confirm that such an attack had been planned, and the threat should pose no immediate danger.
He said that the threat warning was a routine matter, issued out of "an abundance of caution".
The threat called for internet based attacks on financial institutions in the US beginning today, and lasting up until the New Year.
The call also appeared to be in response to the holding of prisoners accused of terrorism in the US's Guantanamo Bay camp.
The warning was issued by the Homeland Security Department's computer emergency readiness team - responsible for warning web-based businesses about new internet security threats.
US stock market electronic security was increased significantly following the September 11th attacks in 2001.