Mizuho Bank, eBank and Japan Net Bank were all hit on Tuesday, Terunobu Maeda, the head of the Japanese Bankers Association revealed.
"Yeah, I lost money over this spyware bug, lets just say about 500 in U.S. dollars," said one irate customer in a forum. "I'm sure most of the people targeted were foreigners."
The money was taken from nine different bank accounts, Maeda said.
"Every day we see more attempts to spy on innnocent users by organised criminal gangs focused on stealing money," said Graham Cluley, senior technology consultant at antivirus company Sophos. "Banks are especially anxious that users do not lose faith in using the internet to access their accounts because it is a cheaper and more flexible way for them to do business with their customers."
Earlier in July SC Magazine reported a group of software companies, ISPs, security suppliers, and public-interest organizations has drafted a definition of spyware in the hopes of better tackling the sneaky software.