More than six out of 10 ATM machines in the country will be running on an obsolete operating system when Microsoft pulls the plug on Windows XP support on April 8, raising serious security and compliance issues for the systems' operators.

According to the ATM Industry Association (ATMIA), about 38% of the nearly 425,000 ATMs in the U.S. that are powered by Windows XP will have migrated off the OS by next month's deadline.

Operators of the remaining quarter million or more machines will have an increasingly hard time supporting their systems and ensuring sufficient software security after that date.

The Payment Card Industry Security Standards Council (PCI SSC), which is responsible for overseeing security standards in the payments industry, has already noted that ATMs still on Windows XP after April 8 will need to have certain compensating controls in place to be considered PCI compliant. The PCI SSC estimates that Windows XP powers 95% of ATMs in the world.

"The vast majority [of ATM operators] are aware of the deadline," said David Tente, executive director USA of the ATMIA.

Many operators have already moved or are in the process of moving their systems to Windows 7, which is the next available Windows upgrade for ATM systems, Tente said. But for a majority, the cost and time involved in upgrading their systems to a new OS is a huge challenge, he said.

Several financial institutions have worked out, and at great cost, arrangements with Microsoft to keep Windows support available for a while longer, he said.

In many cases, upgrading an ATM's operating system involves physical access to the machine and about one hour's worth of labor. Not all ATMs will be ready to migrate to Windows 7 and may need hardware upgrades as well, Tente said.

According to Tente, independent operators run about half the ATMs in the U.S., while large financial networks operate the rest. A "fair number" of installed ATMs are powered by Windows CE and embedded versions of Windows XP, which are not affected by the April 8 deadline, he said.

Microsoft has said that it will cease support for Windows XP after April 8. After that date, the company will stop providing security updates or technical support for Windows XP, an operating system that still has a huge installed base around the world.

Microsoft has pointedly stated that PCs running Windows XP after the end-of-support date should not be considered protected and has urged users of the operating system to move to a newer version as soon as possible.

According to Tente, it's possible that malicious hackers are waiting until after April 8 to attack ATMs and other systems running Windows XP. But just because a system remains on Windows XP after that date does not automatically make it more vulnerable.

"An ATM on April 9th is going to be just as secure as it was on April 7th," if operators have the proper measures in place for protecting them, Tente said.

The ATMIA earlier this month released a white paper outlining several of the risks that operators face by choosing to remain on Windows XP. The paper is available only to registered members of the association.

An executive summary provided to Computerworld highlighted several issues. Since Windows XP was launched, more than 700 vulnerabilities have been found in the operating system.

"After April 8th 2014, Windows XP will essentially have zero-day vulnerabilities for perpetuity," the statement noted.

Most ATM hacks have been at the hardware level and through the use of devices like skimmers. Other security risks include attacks on an ATM's network, local ports, or browser, the summary said.

Without Microsoft's technical support and security fixes, ATM operators also risk falling out of compliance with requirement 6.2 of the PCI DSS, which stipulates that all system components handling credit and debit cards are fully supported by a software or hardware vendor.

"If a vendor isn't providing patches due to support having been discontinued, then by definition that system cannot be PCI DSS compliant," said Jim Huguelet, an independent retail security consultant. "As a general rule, retailers would be concerned about running any systems without access to ongoing security analysis and patches, but it is PCI DSS requirement 6.2 that brings the issue to the forefront."

A joint statement issued by the PCI SSC and the ATMIA pointed to several compensation controls that ATM operators can implement to remain compliant with PCI requirements even while remaining on Windows XP.

"To be effective, the compensating controls must protect the system from vulnerabilities that may lead to exploit of the unsupported code," the statement said.

Examples of controls that could be combined and used to mitigate risk include active monitoring of system logs and network traffic, application whitelisting and isolating Windows XP systems from other systems and networks. Each control by itself is insufficient, but when combined, could potentially qualify as a compensating control from a PCI compliance standpoint.

"Compensating controls should only be considered a temporary solution," Troy Leach, CTO of the PCI SSC, said in the statement. "Organizations should have a migration plan to upgrade in a reasonable amount of time to a supported operating system as the OS serves as the foundation for services and other security controls related to protecting cardholder data."

This article, Majority of ATMs will remain on Windows XP after Microsoft's pulls plug on OS support, was originally published at Computerworld.com.

Jaikumar Vijayan covers data security and privacy issues, financial services security and e-voting for Computerworld. Follow Jaikumar on Twitter at @jaivijayan or subscribe to Jaikumar's RSS feed . His e-mail address is jvijayan@computerworld.com.

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