Investigators working on the cyberattack at JPMorgan Chase have found clues that a global network of computers available for hire was used to send the stolen data to a Russian city, Bloomberg reported, citing people familiar with the ongoing probe at the bank.
JPMorgan's own investigators have identified what they believe to be the assault's staging ground, called a "bulletproof" hosting platform because of its resilience to other attackers and to law enforcement, the report said.
The attackers used a network of servers that are commandeered without their legitimate owners' knowledge through hacking or fraud, according to the report.
The report said a spokesman for President Vladimir Putin dismissed any Russian involvement in the attack.
JPMorgan last week said it was working with law enforcement authorities to determine the scope of the attack. It disclosed the probe after the FBI said it was investigating media reports about several U.S. financial companies becoming victims of recent cyberattacks.
JPMorgan was not immediately available for comment outside regular U.S. business hours.