The Big Four Australian banks are pushing ahead with experiments in cloud technology with the expectation that the technology will quickly become a core part of their infrastructure.Cloud technology uses internet-based systems that provide computing power and data storage as needed.The across-the-board push towards cloud technology is continuing even as the Australian Prudential Regulatory Authority reiterates its tight conditions for the use of cloud services. APRA said this week that banks using the technology must be "fully aware of the risks involved." And they must make "a conscious and informed decision as to whether the additional risks are within its risk-appetite." The Big Four have all decided to one extent or another that the risk is worth taking.Bank IT leaders have all stressed the economy and agility of cloud solutions, which will allow them to ratchet up access to computing power on demand, and scale it down at the end of a project or campaign.While they are heading in the same direction, each bank's approach has different nuances. The NAB has so far concentrated its efforts on "private cloud" solutions - that is, solutions that may be managed by an outside partner but are operated solely for the bank. CBA, Westpac and ANZ are all experimenting with "public cloud" solutions that are available to any paying customer and are operated by firms such as Amazon and Rackspace.CBA: Cloud enthusiastCBA began developing cloud strategies five years ago and now runs a series of websites on the Amazon Web Services' cloud. CBA's chief information officer, Michael Harte, argues enthusiastically that it is time for banks and other enterprises to "stop hiding behind all the old excuses" and embrace the cloud.The faster people get into it, the more stable the digital economy will be, he said last month.Although the bank has no plans to host customer data in the public cloud, Harte claimed that CBA's security requirements were more stringent than those of the Australian government when it reviewed different cloud platforms. What is particularly compelling for the banks are the economics of cloud computing. Harte explained clouds promised up to 40 per cent savings compared with more traditional on-premises infrastructure. "There is no point in running our own infrastructure… for utility purposes," he said.The agility that the cloud can deliver is also important. CBA claims that while it used to take eight weeks and thousands of dollars to commission a physical server for an application it takes as little as eight minutes, at a cost of just 25 cents, using Amazon's Sydney-based cloud facility, which opened last month.NAB: Private cloud standard-setterNAB has taken a leadership role in cloud technology standards as one of just 13 international foundation members of the Open Data Centre Alliance. The ODCA was established to develop and promulgate cloud computing standards worldwide, and NAB is leading the testing of a cloud security model for the group.Closer to home, NAB is working with IBM and Telstra on the development of an infrastructure-on-demand environment - essentially, a private cloud. Gavin