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Attack hijacks sensitive data using newer Windows features

Mac OS X probably vulnerable too

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Security researchers have outlined a way to hijack huge amounts of confidential network traffic by exploiting default behavior in Microsoft's Windows operating system.

The MITM, or man-in-the-middle, attacks described on Monday take advantage of features added to recent versions of Windows that make it easy for computers to connect to networks using the next generation IPv6 protocol. The attack will also work against Apple's OS X for Macs, although the proof-of-concept has not been tested on that platform, said Jack Koziol, a program manager at InfoSec Institute, an information security services company.

The attack exploits an industry standard known as SLAAC, or Stateless Address Auto Configuration for allowing clients and hosts to find each other on IPv6 networks. When the next-generation addressing scheme is turned on, as it is by default in OS X, Windows Vista, Windows 7 and Server 2008, SLAAC can be used to create an unauthorized IPv6 network that reroutes data through hardware controlled by the attackers.

“All these Windows boxes will default connect to the evil router instead of the legitimate router when this parasitic overlay is running,” Koziol told The Register. “If Microsoft didn't have that configuration by default, it would negate a lot of the effects of the attack.”

The proof of concept outlined by Infosec Institute researcher Alec Waters requires no interaction at all from end users and provides no warning that their machines are connecting to an unauthorized IPv6 network.

The technique works because the vulnerable operating systems automatically prefer to use the newer protocol over the older one. Implanting a rogue piece of hardware that uses IPv6 in an IPv4-based network will cause the computers to automatically route traffic over the unauthorized device and bypass the legitimate channels. In other words, the attack works by altering the flow of traffic over the targeted network by exploiting the OS's preference to use the newer protocol over the older one.

By default, Linux, FreeBSD and other operating systems aren't vulnerable, Koziol said.

The technique has long been considered a theoretical means of hijacking network traffic, in the same vein as poisoning data associated with the so-called Address Resolution Protocol. But while there are plenty of tools for detecting and preventing ARP attacks, there are virtually none for countering the effects of SLAAC attacks, Koziol said. What's more, with the growing adoption of newer versions of Windows and OS X, the attacks will work by default on an increasing number of machines.

Of course, attackers will still need to figure out a way to sneak a rogue piece of hardware into a network. But in environments that are already vulnerable to insider threats, the support of Microsoft and Apple could make the attack feasible where it wasn't before.

Bruce Cowper, group manager in Microsoft's Trustworthy Computing group issued the following statement:

"Microsoft is aware of discussions in the security community concerning the possibility of using IPv6 network protocols to undertake a 'man in the middle' attack on a target network. The attack method described would require that a would-be attacker have physical access to the targeted network in order to install a tainted router - a situation that does not provide a security boundary."

The only way to prevent the attack for now is to disable IPv6 on all machines that don't use the protocol. ®

This article was updated to include comment from Microsoft.

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