With Windows 7, Microsoft pledged to go the OS X route on this topic, tuning down the UAC's warnings to a lesser level.  Many security firms complained about this approach and Microsoft relented slightly, restoring some of the UAC's warnings, in particular a warning about the disabling the UAC altogether (experts showed that attackers could disable the UAC without prompting the user in early builds of Windows 7).

While these changes helped make Windows 7's release edition more secure than the test builds, the UAC's default setting is still neutered compare to Vista's robust solution, indicates Sophos Senior Security Adviser Chester Wisniewski.  He's just completed a study of attacking Windows 7 with malware and seeing how the new UAC responds.

Of the ten pieces of malware tested, Windows 7 wouldn't install two of them.  Of the remaining eight only one generated a UAC warning, allowing the user to disallow its installation.

Microsoft officials, though, minimized the test, saying the UAC just isn't that important a security feature anymore.  They point to Windows 7's improved memory protections and Microsoft free Security Essentials antivirus suite as two critical tools that can be used to fight infection, in addition to the UAC. 

States a Microsoft spokesperson, "Windows 7 is built upon the security platform of Windows Vista, which included a defense-in-depth approach to help protect customers from malware; this includes features like Security Development Lifecycle (SDL), User Account Control (UAC), Kernel Patch Protection, Windows Service Hardening, Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP)."

"Windows 7 retains all of the development processes, including going through the Security Development Lifecycle, and technologies that made Windows Vista the most secure Windows operating system ever released," the spokesperson added. "Coupled with Internet Explorer 8—which includes added malware protection with its SmartScreen Filter—and Microsoft Security Essentials, Windows 7 provides flexible security protection against malware and intrusions."

While he understands that with other supplemental protections Windows 7 will likely be safe, Mr. Wisniewski seems mildly disapproving of defaulting the UAC to reduced functionality.  After all, users of Windows Vista may be lulled into a false sense of security expecting prompts to save them from malware.  Ultimately, though, there's little that can be done to convince Microsoft to change this, though, and he concludes, "Lesson learned? You still need to run antivirus [protection] on Windows 7."