Banks risk exposing customer data to hacking attacks in deploying mobile-phone ATM applications, warns independent security consultancy SecureTest. Up to 20 high street banks in the UK are gearing up to roll-out balance request and mobile phone top-ups using the service, dubbed MobileATM, by the end of the year.

The service features security functions such as a two-step authentication procedure, developed following the roll-out of similar mobile applications in the online gambling sector, by developer MChex. The technology features security software which requires the user to enter their PIN and a one-time password to authorise transactions.

The server-side security of this system has reportedly been subjected to a risk assessment. But SecureTest reckons it may be possible for a hacker to sidestep security defences by hacking into the source code of downloaded applications and altering it to suit their malicious intentions. Such an approach would create a means for hackers to infiltrate and manipulate the application server, it claims, potentially gaining access to confidential data. If breached, data such as user log-ins or passwords, bank account details and other personal information can be harvested. Once transactional services are added, hackers could even use the application to siphon cash into other accounts, the consultants say.

SecureTest bases this warning on tests of other mobile Java applications on behalf of several clients in the mobile gambling market rather than on the MobileATM service, which it hasn't tested. Ken Munro, managing director of SecureTest, said the comparison is appropriate because the same type of technology and distribution methods are applied in both cases.

Many mobile phone applications are written in Java 2 Mobile Edition (J2ME), allowing code to be ported between different handsets models. However, this approach also makes it relatively simple to decompile the application to its source code, according to SecureTest. A hacker could intercept the mobile application during the download process, use freeware tools on a PC to gain access to the application source code, remove security features and reload the software.

"Freeware decompilers make Java applications easy to exploit by hackers. Anybody able to code Java might be able to do this. Unless the bank has strong server-side validation, these mobile applications can and will be used to harvest sensitive information and, once the banks add transactional capabilities, they risk losing customers' money," he said.

SecureTest has come across content and input validation security weaknesses in around half the mobile gambling applications it has tested. These potential security loopholes range from less serious information leakage flows to more serious vulnerabilities. "We're not accusing MChex of planning to release flaky software but we do want to warn of examples in problems with similar technology in different verticals," Munro told El Reg.

MobileATM is being offered to banks by cash machine operator LINK. It will initially be available only in a limited form (offering only balance checking and mobile top ups) but LINK and MChex are considering the inclusion of functions such as cash transfers or the ability to extend overdraft limits by as early as the end of the year. Further m-commerce services such as person-to-person payments and retail purchases may be added at a later date.

MChex declined our invitation to comment on the security concerns raised by SecureTest. SecureTest has produced an explanation of mobile security risks and advice on how to avoid exploits here. ®

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