Quarantine PCs to Fight Botnets, Microsoft Says

Microsoft's security chief last week pitched a plan that would block some botnet-infected computers from connecting to the Internet.

A noted botnet researcher said the proposal didn't attack the problem at its root, and like many technical solutions, was unlikely to do much good.

In a paper published Wednesday, Scott Charney, who heads Microsoft's trustworthy computing group, spelled out a concept of "collective defense" that he said was modeled after public health measures like vaccinations and quarantines.

Under Charney's proposal, PCs would be issued a "health certificate" that showed whether the system was fully patched, that it was running security software and a firewall, and that it was malware-free. Machines with deficiencies would require patching or an antivirus update, while bot-infected PCs might be barred from the Internet.

Quarantining PCs could be a last-step measure, Charney said, to keep compromised PCs from threatening others on the Web.

"Just as when an individual who is not vaccinated puts others' health at risk, computers that are not protected or have been compromised with a bot put others at risk and pose a greater threat to society," Charney argued in a post to a company blog . "We need to improve and maintain the health of consumer devices connected to the Internet in order to avoid greater societal risk."

Charney admitted that his proposal would face resistance, such as privacy concerns, over what the health certificate would reveal and whether it would be tied to a specific individual. Even so, he made suggestions likely to raise a ruckus.

"There may be value in uniquely identifying devices, as when a device may be infected on a home network," he wrote in his paper, Collective Defense: Applying Public Health Models to the Internet ( download PDF ). "It may also be possible, of course, to combine device information with other information to identify a user (much like cell phones may have unique identifiers and can be tied to particular account holders)."

Charney also said that government intervention would be necessary, another issues the notoriously anti-regulation Internet community may balk at. "Voluntary behavior and market forces are the preferred means to drive action but if those means fail, then governments should ensure these concepts are advanced," he said.

The bottom line is that current methods to block criminals from infecting consumers' computers are not working, news that may come as a surprise to Microsoft 's own Malware Protection Center, which regularly touts the success of its Windows Malicious Software Removal Tool, a free program that scrubs infected Windows systems.

"Commonly available cyber defenses such as firewalls, antivirus and automatic updates for security patches can reduce risk, but they're not enough," Charney said. "Despite our best efforts, many consumer computers are host to malware or are part of a botnet."

Botnets are collections of already hijacked computers that criminals use as a force multiplier to send spam, host malware or launch distributed denial-of-service attacks against Web sites. A botnet may consist of only hundreds of individual PCs, more likely thousands, and in rare cases, millions.

Carney's ideas are neither new nor untested, as he pointed out in his paper. For example, Comcast, the largest residential Internet service provider in the U.S. with an estimated 16.4 million subscribers, recently announced it would notify customers when it detected a bot on their machines. Comcast will direct infected users to a site that walks them through a malware clean-up chore.

But it's unlikely Charney's ideas will curtail botnets or even pass muster with users, said Joe Stewart, director of malware analysis at Atlanta-based SecureWorks, and a well-known botnet expert.

"If you don't address the human behind the botnet, you'll fail," Stewart said.

"Technical solutions just haven't worked," Stewart said, referring to Charney's health certificate concept. Criminals are simply too adaptable, too clever to be long stymied by any technology-based defense, whether certificates -- which even Charney acknowledged would have to be counterfeit-proof -- or antivirus software, firewalls and patches.

"Plenty of people get infected by a bot who have all the patches, who have a firewall, who have antivirus," Stewart said. "They don't even know they've been infected." How, then, would one explain to them that they can't get on the Internet? he asked.

Instead, more resources should be dedicated to other initiatives. "First, we need much better global communication and collaboration" between researchers and law enforcement, he said, as well as an enforceable way to hold ISPs accountable for hosting botnets' command-and-control servers, no matter where they're located.

"And we need more what I call 'offense in depth,'" Stewart added, explaining the strategy as one where researchers and law enforcement agencies hound a botnet until its gang of controllers is driven out of business or arrested.

Stewart has proposed that before. Last April he laid out an anti-botnet approach in which teams of paid security researchers, similar to a police department's major crimes unit, would stalk and disrupt specific criminal gangs or botnets.

Even if Charney's technology-based proposal worked, Stewart was skeptical that people would buy into the idea.

"I just don't see how you could make it happen with the current paradigm of computing," said Stewart. People are accustomed to the idea that they can do what they want with their personal computer -- put any software on the machine, jump on the Internet at a moment's notice -- and a radical departure from that will have a tough time finding supporters.

The only way to block botnets from getting on PCs is if the PC industry adopted a closed ecosystem, similar to Apple 's App Store, said Stewart, where only certain applications are allowed to be installed.

"But everything would have to be fundamentally redesigned," he said. "I don't think people have reached the point yet with botnets where they would agree to that. Maybe in 20 years. But for now we're locked into this mentality that we can do anything we want."

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer or subscribe to Gregg's RSS feed . His e-mail address is gkeizer@computerworld.com.

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