[ISN] Vista security overhaul questioned

From: InfoSec News (alerts@private)
Date: Mon Feb 19 2007 - 23:16:08 PST


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 
user mode.

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 
admin credentials.

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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