BitLocker, TPM won't defend all PCs against VBootkit 2.0

Trusted Platform Modules and BitLocker Drive Encryption can protect Windows 7 computers against a bootkit attack unveiled last week but these technologies won't be available on a large portion of computers, leaving millions of users unprotected when Microsoft releases its next version of Windows.

VBootkit 2.0 is proof-of-concept code that was unveiled by security researchers Vipin Kumar and Nitin Kumar, of NVLabs, at the Hack In The Box (HITB) security conference held in Dubai last week. The code, which is just 3KB in size, allows an attacker to take control of a Windows 7 computer by patching files as they are loaded into the system's main memory. Because no software is modified on the computer's hard disk, the attack is nearly undetectable.

VBootkit 2.0 is an updated version of an earlier tool, called VBootkit 1.0, that can take control of a Windows Vista computer by a similar method.

With VBootkit 2.0, once an attacker has taken control of the Windows 7 computer during the boot process they are able to get system-level access to the computer, the highest level possible. They can also remove user passwords to gain access to protected files and strip DRM (digital rights management) protection from multimedia files. The passwords can then be restored, hiding any evidence that it was compromised.

"There's no fix for this. It cannot be fixed. It's a design problem," Vipin Kumar said during his presentation last week, referring to Windows 7's assumption that the boot process is safe from attack.

In response, a Microsoft representative said Windows 7's support for Trusted Platform Module (TPM) and BitLocker Drive Encryption (BDE) means the attack is "void," downplaying the threat to users.

That assertion is partly correct. TPMs are microcontrollers that contain encryption keys and digital signatures, adding an extra level of security through hardware authentication of software files. BDE is a data-protection feature available in some versions of Windows Vista that works by encrypting data on a computer's hard disk. These are powerful protections that defend against bootkit attacks but they are not available on all computers.

"TPM and BitLocker (collectively) would stop VBootkit from working. But TPM is not available on consumer PCs -- most of the them -- and BitLocker is available only in high-end Vista editions," Nitin Kumar wrote in an e-mail.

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