Tuesday, November 29, 2011

Millions of printers open to devastating hack attack, researchers say

Columbia University

This time-lapsed image of a screen on an HP LaserJet shows the impact of a rogue print job used to reprogram the device.

Could a hacker from half-way around the planet control your printer and give it instructions so frantic that it could eventually catch fire? Or use a hijacked printer as a copy machine for criminals, making it easy to commit identity theft or even take control of entire networks that would otherwise be secure?

It’s not only possible, but likely, say researchers at Columbia University, who claim they've discovered a new class of computer security flaws that could impact millions of businesses, consumers, and even government agencies.

Printers can be remotely controlled by computer criminals over the Internet, with the potential to steal personal information, attack otherwise secure networks and even cause physical damage, the researchers argue in a vulnerability warning first reported by msnbc.com.  They say there's no easy fix for the flaw they’ve identified in some Hewlett-Packard LaserJet printer lines – and perhaps on other firms’ printers, too – and there's no way to tell if hackers have already exploited it.

The researchers, who have working quietly for months in an electronics lab under a series of government and industry grants, described the flaw in a private briefing for federal agencies two weeks ago. They told Hewlett-Packard about it last week.

HP said Monday that it is still reviewing details of the vulnerability, and is unable to confirm or deny many of the researchers’ claims, but generally disputes the researchers’ characterization of the flaw as widespread.  Keith Moore, chief technologist for HP's printer division, said the firm "takes this very seriously,” but his initial research suggests the likelihood that the vulnerability can be exploited in the real world is low in most cases.      

“Until we verify the security issue, it is difficult to comment,” he said, adding that the firm cannot say yet what printer models are impacted.

But the Columbia researchers say the security vulnerability is so fundamental that it may impact tens of millions of printers and other hardware that use hard-to-update “firmware” that’s flawed.

'Crystal clear'

The flaw involves firmware that runs so-called "embedded systems" such as computer printers, which increasingly are packed with functions that make them operate more like full-fledged computers. They also are commonly connected to the Internet. 

"The problem is, technology companies aren't really looking into this corner of the Internet. But we are," said Columbia professor Salvatore Stolfo, who directed the research in the Computer Science Department of Columbia University’s School of Engineering and Applied Science. “The research on this is crystal clear.  The impact of this is very large. These devices are completely open and available to be exploited.”

Printer security flaws have long been theorized, but the Columbia researchers say they've discovered the first-ever doorway into millions of printers worldwide.  In one demonstration of an attack based on the flaw, Stolfo and fellow researcher Ang Cui showed how a hijacked computer could be given instructions that would continuously heat up the printer’s fuser – which is designed to dry the ink once it’s applied to paper –  eventually causing the paper to turn brown and smoke.

In that demonstration, a thermal switch shut the printer down – basically, causing it to self-destruct – before a fire started, but the researchers believe other printers might be used as fire starters, giving computer hackers a dangerous new tool that could allow simple computer code to wreak real-world havoc.

Cui and Stolfo say they've reverse engineered software that controls common Hewlett-Packard LaserJet printers. Those printers allow firmware upgrades through a process called "Remote Firmware Update." Every time the printer accepts a job, it checks to see if a software update is included in that job.  But they say printers they examined don't discriminate the source of the update software – a typical digital signature is not used to verify the upgrade software’s authenticity – so anyone can instruct the printer to erase its operating software and install a booby-trapped version.

In all cases, the Columbia researchers claim, duping a would-be target into printing a virus-laden document is enough to take control of that person's printer; but in some cases, printers are configured to accept print jobs via the Internet, meaning the virus can be installed remotely, without any interaction by the printer's owner.

“It's like selling a car without selling the keys to lock it,” Stolfo said. “It’s totally insecure.”

Columbia University

Columbia researcher Ang Cui explains how he was able to infect an HP printer with malicious code.

Rewriting the printer's firmware takes only about 30 seconds, and a virus would be virtually impossible to detect once installed. Only pulling the computer chips out of the printer and testing them would reveal an attack, Cui said.  No modern antivirus software has the ability to scan, let alone fix, the software which runs on embedded chips in a printer.

“First of all, how the hell doesn't HP have a signature or certificate indicating that new firmware is real firmware from HP?” said Mikko Hypponen, head of research at security firm F-Secure, when told of the flaw. “Printers have been a weak spot for many corporate networks.  Many people don’t realize that a  printer is just another computer on a network with exactly the same problems and, if compromised, the same impact.”

There are plenty of points of contention between HP and the researchers, however. Moore, the HP executive, said the firm’s newer printers do require digitally signed firmware upgrades, and have since 2009. The printers tested by the researchers are older models, Moore said. 


In contrast, the Columbia researchers say they purchased one of the printers they hacked in September at a major New York City office supply store.

Moore also said that the impact of any potential vulnerability is limited because most home users have InkJet printers – not LaserJet printers – and they do not permit remote firmware upgrade, he said.

Still, a widespread flaw in LaserJet printers would raise serious issues. Hewlett Packard dominates the printer market; the firm says it's sold 100 million LaserJet printers since 1984, meaning millions of computers could be vulnerable. HP, by far the dominant printer seller worldwide with 42 percent of the market, sells about 50 million printers of all kinds annually, according to IDC.

In an exclusive demonstration for msnbc.com at Columbia University’s Intrusion Detection Systems Laboratory, Cui and Stolfo revealed the kind of havoc an attacker could wreak once they gained control of a printer. After sending a virus-laced print job to a target printer, the device's small screen read, in sequence, "Erasing...Programming...Code Update Complete."

In one demonstration, Cui printed a tax return on an infected printer, which in turn sent the taxform

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