According to reports in the Financial Times, the gang managed to hack into the bank's computer system last October and tried to transfer money to ten bank accounts worldwide. They installed keylogging software on computers within the corporation to track the passwords of Sumitomo staff and gain access to secure areas in order to drain funds from the financial institution.
Police in Israel are said to have arrested a man whose account had been the intended recipient of some of the money. This came after the plot to steal money was uncovered by the UK's National Hi-Tech Crime Unit (NHCTU).
Sumitomo's head of communications in Tokyo, Takashi Morita, told the Press Association the bank had not lost any money after the attempted robbery. "We have undertaken various measures in terms of security and we have not suffered any financial damage," he said.
Steve Purdham, SurfControl CEO, said the news must act as "a wake-up call for the banking and finance sector and business in general as to the potential damage that spyware can cause."
"Spyware is by no means a new threat and has been around in various forms for a number of years, but the difference now is that the criminal community is now starting to exploit it to its advantage," he said.
Arthur Barnes, security consultant at Diagonal Security said this heralded the start of companies being more open about security incidences.
"Sumitomo has gone public to let people know they know who has committed this crime," said Barnes. "The NHCTU has had some very high profile successes lately and it has done a great job in getting Sumitomo to go public."