Microsoft 'neutered' UAC in Windows 7, says researcher

Blocks only 1 out of 8 Trojans from executing, claims Sophos

Microsoft Corp.'s decision to reduce the number of annoying security messages that Windows 7 delivers when users install software makes the new operating system more vulnerable to malware infection than Vista was, a researcher said today.

"UAC was neutered too much by Microsoft," argued Chester Wisniewski, a senior security adviser at Sophos PLC, talking about User Account Control (UAC), a Windows security feature that Microsoft debuted with Vista.

UAC prompts users for their consent before allowing a task such as the installation of a program or a device driver to take place. In an attempt to quash user complaints about the constant intrusions, Microsoft modified UAC so it appears less frequently in Windows 7.

That wasn't a good idea, said Wisniewski.

"We wanted to know if UAC was going to be effective in Windows 7," he said. "So we grabbed the next 10 [malware] samples that came in and tried them out."

The 10 samples, most of them Trojan horses, were loaded onto a clean Windows 7 PC that lacked antivirus software, simulating payloads that an actual exploit would deposit on a compromised computer. Wisniewski then ran each piece of malware -- as if a user had been duped into launching a file attachment or had surfed to a malicious site and been victimized by a drive-by attack and subsequent silent download.

Two of the 10 samples would not run under Windows 7 (probably because they were designed to execute on the far-more-common Windows XP and Vista), and of the remaining eight, only one triggered a UAC prompt, said Wisniewski.

He acknowledged that the test was just a quick-and-dirty exercise that didn't accurately portray how secure Windows 7 was overall -- or how well it would withstand attack if it was protected by even a basic antivirus tool like Microsoft's free Security Essentials. The point was to see how much Windows 7's reconfigured UAC would help block malware that made it past security software or got by the operating system's other defense mechanisms, like DEP (Data Execution Protection) and ASLR (Address Space Layout Randomization).

"UAC is really not protecting users properly," Wisniewski said. "Frankly, people should turn it back into the more aggressive mode, like Vista," he said, referring to the fact that users have the ability to set the frequency of UAC alerts. "And if you find it annoying, you might just as well turn it off, because otherwise it's not doing any good."

UAC's effectiveness has been questioned before. Last February, for instance, a developer for a Virginia-based company that sells secure messaging software to the U.S. government and a well-known blogger claimed that a change to UAC 7 could be exploited by attackers to secretly disable the feature. Microsoft first denied that that aspect of the software was a bug, saying instead that it was by design. But it later backpedaled and promised to fix the problem.

Copyright © 2009 IDG Communications, Inc.

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