German researchers have devised five methods that determined attackers can use to bypass hard-drive encryption in recent versions of Microsoft operating systems.
The methods, laid out by a research team from the Frauenhofer Institute for Security Information Technology, can be used to access files protected by BitLocker drive encryption contained in Windows Server 2008 and pricier versions of Windows Vista and Windows 7. BitLocker prevents files or entire volumes from being accessed without a user password being entered first.
The researchers stress that the strategies are useful only for targeted attacks, such as those used in industrial espionage, where an attacker is willing to devote considerable effort to breaching a single individual's security.
They aren't of much use in opportunistic attacks, such as those when an attacker happens upon a lost laptop. Still, they said their findings are useful because they demonstrate the limits of the protection.
"Designers as well as users of disk encryption solutions should be aware of these attack strategies in order to realistically assess how much security they get out of trusted computing," they wrote. "The most important lesson to be learned is that even with trusted computing a system needs additional physical protection for good security."
Among the methods discussed is what they call a "hardware-level phishing attack," in which a target machine is replaced with a counterfeit one that provides precisely the same messages and prompts that the original machine would have produced. The imposter machine captures user input and relays it to the attacker, who then uses it on the real machine.