It appears to be an inside job, as it uses undocumented functions of the ATM software and appears to use the printer. This suggests the people behind the malware have access to the Diebold software (perhaps as a result of disassembling the code from an actual ATM) as well as physical access to one or more operational ATMs.
Maybe it wasn't such a good idea to liberalise the ATM market. When they were the exclusive domain of banks and similar financial institutions, you could be confident that the people involved had been reasonably well vetted.
But the outsourcing of routine maintenance such as loading the machines with cash, plus the spread of third-party ATMs means we can no longer be quite so confident that everyone that has access to the devices is an upstanding citizen.
According to Sophos, the malware is a Trojan - which implies that it must be explicitly run on the target system, as opposed to a worm that might find its way in over a network.
Apparently the code 'skims' the details read from the magnetic card, logs the PIN entered by the user, parses the transaction details, and prints the stolen data.
How might the malware get into an ATM? Please read on.
You can imagine a scenario where a corrupt ATM replenisher runs the Trojan, then on the next visit collects the printout - and possibly cleans out the malware to minimise the risk of detection.
Sophos has also hypothesised that the stolen information may be encrypted for local storage until a specially-coded card is inserted, which triggers a printout of the card details and PINs.
Another possibility, according to the company, is that the Trojan was intended to be installed by someone with access to the ATMs during the manufacturing process.
(There were reports last year that hundreds of 'chip and pin' EFTPOS devices shipped to European stores had been fitted with covert hardware that forwarded card details to Pakistan via mobile phone.)
The good news - for most of us, anyway - is that "it appears that the malicious code is designed to skim money from accounts in Russian, Ukrainian and American currency," according to Sophos's Graham Cluley.
If your account isn't based on one of those currencies, a 'foreign' transaction should be particularly obvious on a statement or a transaction list obtained via Internet banking.
Just one more reason to keep a close eye on your accounts!