The four major banks have proven uncharacteristically taciturn in response to suggestions that the security of their online banking systems may be at risk.Recent revelations that Western security agencies may have managed to crack supposedly secure layers of the internet used to encrypt and protect online banking data led to local security experts recommending this week that banks review and possibly upgrade their security practices.However the banks - which usually trumpet their security credentials - have been almost mute on the issue.NAB was the most loquacious, with a spokesman saying that "organisations can't afford to sit still on web-based threats. NAB is continually updating its approach to keep on the front foot."NAB employs a combination of technology and investigative intelligence to maintain safe, easy and reliable banking for customers. As an early adopter and innovator of many new technologies, NAB ensures its cyber security remains in the strongest viable position."It is this belt-and-braces approach, which relies on a combination of technology, people and processes, that security experts stressed this week was the best way to protect online data.ANZ, famous for its Falcon advertising, which stresses the importance the bank places on customer security, responded only with a statement that the bank supports the move towards Secure Sockets Layer 256-bit encryption.Commonwealth Bank declined to comment on the issue at all, while Westpac has yet to respond to Banking Day's inquiries.While no-one would expect the banks to explain in great detail how they protect customer data, lest that insight be used to mount an attack against them, it seems surprising that they are not doing more to allay customer concerns in light of the recent revelations.