By John Leyden
19th February 2007
Security researchers have taken issue with Microsoft's implementation of
a security feature in Vista that is designed to stop users from
routinely running systems in admin mode.
Users of Windows XP and older Microsoft operating systems habitually ran
PCs in admin mode, which gives unrestricted access to the system. As a
result, malware attacks carried the ability to take over compromised
systems which wouldn't normally be possible if a machine was running in
The User Account Control (UAC) security functionality of Windows Vista
is designed to address this problem by obliging users to run their Vista
PCs via a normal user account by default. Users are asked to switch
modes and enter login credentials when they request a task requiring
White hat hacker Joanna Rutkowska discovered that users attempting to
run an installation file need to do so in admin mode. That means users
are confronted with the all-or-nothing choice of granting an installed
program complete system privileges or abandoning an installation
"That means that if you downloaded some freeware Tetris game, you will
have to run its installer as administrator, giving it not only full
access to all your file system and registry," Rutkowska writes, adding
that Win XP gave her the ability to add permissions to her normal
(restricted) user account that isn't possible with Vista.
Mark Russinovich, a technical fellow at Microsoft, argues in a detailed
response that the design of Vista's User Account Control balances
security and usability.
Rutkowska acknowledges that Microsoft has improved the security of its
operating system with Vista but warns that the security shortcomings of
UAC can not be so easily dismissed. "UAC is not perfect [but that]
doesn't diminish the fact that it's a step in the right direction,
implementing a least-privilege policy in Windows OS," she writes.
Rutkowska takes issue with Microsoft's contention that flaws in UAC
controls don't in themselves create security bugs. She points, by way of
example, to a security bug she has discovered which allows a low
integrity level process to send WM_KEYDOWN messages to a command prompt
window running at high integrity level as among the types of problems
she is seeking to highlight.
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