Unsupported Windows XP machines in China could pose a threat to the Internet in general if bot-herders round up significant numbers of them to use as launch pads for malicious exploits, according to a top white-hat hacker.

James Forshaw, a vulnerability researcher for Context Information Security, says the vast number of XP computers in China represents the potential staging ground for attacks if they become compromised.

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"If we're talking tens of millions of machines that's a significant pool to do DoS or other malicious attacks," says Forshaw, who is a $100,000 winner of Microsoft's BlueHat bounty prize for finding and reporting vulnerabilities in its Internet Explorer browser. "It might be in everyone's best interest to get China or other countries to help them to migrate."

StatCounter, which tracks operating system use by country, says that in January Windows XP represented 50.46%  of the operating systems in use in China. That's down from 63% the year before, but still very significant. With China's population upward of 1.3 billion, that represents a lot of machines, Forshaw says.

The cost of migration is cited as the main reason so many Chinese haven't upgraded their operating systems despite Microsoft's alerts that support for XP ends April 8, and perhaps financial incentives from Microsoft would help, he says. For example in the U.S., Microsoft is offering discounts on certain Windows 8 computers if customers trade in XP machines. "It's a question of if they believe it's in their best interest to help," he says.

The danger these XP machines in China represent already exists, says Cesar Cerrudo, CTO at IOActive Labs. "It seems most [XP users in China] never applied security patches," he says. That may be because many were pirated copies of the operating system and so couldn't be updated because they had no documentation. Former Microsoft CEO Steve Ballmer says 90% of Microsoft software used in China, including Windows XP was pirated. That means the bulk of XP computers in China have never been updated and so are ripe for exploitation, he says.

Forshaw agrees. "If the will was there it was already possible anyway," he says.

How vulnerable they actually are depends on the overall risk footprint for the system the hardware, operating system, applications and security, says Paul Royal, a research scientist and associate director of the Georgia Tech Information Security Center. Since the Web is a major way malware makes its way onto computers, the browser used and its security can make a difference, he says, and short-term those that run on XP will still be supported, he says, such as Mozilla's Firefox and Google Chrome.

Attackers seeking an information bonanza by infiltrating newly unsupported XP may be disappointed, he says. He thinks most of government and large corporations have already transitioned to newer operating systems in order to maintain security or they have additional protections in place. "Mature nation-states are not stupid," he says.

That leaves smaller businesses and residential users, but they represent lower-value targets when it comes to compromising important information, Royal says.

Tim Greene covers Microsoft and unified communications for Network World and writes the Mostly Microsoft blog. Reach him at [email protected] and follow him on Twitter @Tim_Greene.

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