The attack only works when the user is logged in as administrator. Log in to Windows 7 as a standard user and try this; from the default setting you can change the slider to "Always prompt," the Vista equivalent, but to make the setting less strict you have to be logged in as administrator. Thus the user lets the attack have another foot in the door by ignoring another important security feature of Windows.
And in fact, almost the whole point of UAC is to let users run as standard users. And if you want to run as Administrator and be protected from this attack, change the UAC setting to Always prompt, as with Vista. It's true that the default user account after an installation is administrator, but Microsoft does encourage users to create and use standard user accounts. And in an enterprise it would be criminal incompetence to let normal users run their desktops as administrator. (But even if you do, there are group policies to control UAC that override user settings.)
UAC is not a security boundary, as Microsoft's Mark Russinovich explained to some confusion in this TechNet Magazine article. A real boundary, like an ACL, for instance, sets actual rules based on policy. UAC is a convenience for the user; it doesn't stop you from running certain programs, it just tells you what they are and gives you the option of not running them. In fact, there are probably many other ways around UAC, and securing them would be a game of whack-a-mole. Microsoft will probably decide not to whack this particular mole, lest it create a precedent that they must whack all the others. This doesn't help anyone.
The technique could be used for far worse things. Control panel has many important system-wide settings in it. You can set user passwords, uninstall software, disable the firewall, and so on. All of this is possible because of the default UAC setting, and you don't have to change that setting to "exploit" it.
The more I think about this problem the less impressed I am with it. It solves little for Microsoft to change the behavior of this one applet and users who are actually concerned about it have plenty of ways to protect themselves. What this episode demonstrates more than anything else is that security is complicated and not every problem is worth solving.
Thanks to Cameron Sturdevant of eWEEK Labs for helping me confirm some of the points in this article.
Security Center Editor Larry Seltzer has worked in and written about the computer industry since 1983.
For insights on security coverage around the Web, take a look at eWEEK.com Security Center Editor Larry Seltzer's blog Cheap Hack