February 17, 2015 - The day after reports of a one billion dollar cyber heist at banks around the world, a PwC poll shows bank bosses are growing increasingly concerned about the threats posed by online criminal gangs.

The survey of 175 bank CEOs identified cyber risks as one of the biggest threats to growth prospects over the coming years, second only to over-regulation in the catalogue of banking bugbears.

Interviewed for the report, Beth Mooney, chairman and CEO of US bank KeyCorp described the rising tide of data breaches as "fightening".

"The sources of where these breaches are coming from; it's no longer two kids in a basement. These are very sophisticated entities doing it for everything from commerce to criminal," she says. "What we are doing to protect data and our clients, in conjunction with other financial institutions and the government, is one of the most important things, because we are into new territory that has significant consequences."

The PwC poll was released a day after Kaspersky Labs reported that up to a billion dollars may have been plundered from 100 banks worldwide in an unprecedented cyber heist by a gang of unknown hackers.

The attacks, which took place in 30 countries over a two-year timeframe beginning in 2013, were perpetrated by a cybercriminal gang with tentacles in Russia, China and Ukraine.

Kaspersky says at least $300 million has been definitively lost in the spate of attacks, but that number could treble as banks try to pin down a series of $10 million transfers since initiated by the gang.

The crooks used a form of malware dubbed Carbanak, which provided access to bank networks and allowed the gang to overcome internal checks and balances by monitoring bank procedures via video surveillance and keystroke logging.

In some instances, actual customer accounts were artificially inflated and large sums transferred to bogus accounts, while in others the money was dispensed at pre-set times and destinations through cash machines under the control of the hackers.