Researcher Reveals 2-Step Vista UAC Hack

By Lisa Vaas  |  Posted 2007-05-16 Print this article Print

The technique uses social engineering to trick the victim into downloading an innocent-looking file that includes a Trojan horse attack.

A Web application developer has uncovered a two-step process (PDF) for exploiting Windows Vistas User Account Control, essentially by having a Trojan piggyback on what could be a legitimate download. Robert Paveza, a senior Web application developer with Terralever, a Web-based marketing company based in Tempe, Ariz., published details of the vulnerability in a paper titled "User-Prompted Elevation of Unintended Code in Windows Vista." Paveza said in the paper that the vulnerability uses a two-part attack vector against a default Vista installation. The first step requires that malware called a proxy infection tool be downloaded and run without elevation. That software can behave as the victim expects it to while it sets up a second malicious payload in the background.
"For instance, if users believe they are downloading a Pac-Man clone, such a game could be run while the malicious software did its work in the background," Paveza said. He noted that the infection succeeds, for all intents and purposes, with the installation of the proxy infection tool.
"This pattern of infection follows the typical Trojan horse model, piggybacking on what may be otherwise legitimate software," he said. For advice on how to secure your network and applications, as well as the latest security news, visit Ziff Davis Internets Security IT Hub. News of the vulnerability first broke May 15. When eWEEK that day contacted Microsoft, based in Redmond, Wash., a spokesperson said the company is aware of demonstrations that "purport" to show how a Vista system can be attacked. But, the spokesperson said, the demonstration provided by Paveza is of actions an attacker can take on a system that already has been compromised by another means. "With this in mind, it is important to note that user interaction is required for the initial infection of the Trojan to occur," the spokesperson said. "The user must open the attackers malicious executable. Furthermore, the successive social engineering attempt will only be successful if the user inadvertently clicks on the malicious shortcut. In fact, at this point, the user must be part of the local administrators group or provide administrator credentials at the UAC prompt." The spokesperson went on to point to Microsofts previous communications regarding running as a standard user. "Remember that running as a standard user does not prevent malicious software from copying itself to locations controlled by this user, such as the users profile directory," Michael Howard and David LeBlanc noted in "Writing Secure Code for Windows Vista." As far as UAC being vulnerable to social engineering attacks goes, thats old news. Joanna Rutkowska offered constructive criticism of UAC in her blog on Feb. 4, and Ollie Whitehouse, a research scientist for Symantec, based in Cupertino, Calif., followed with a Feb. 20 posting titled An Example of Why UAC Prompts in Vista Cant Always Be Trusted. Shortly thereafter, a Microsoft spokesperson told eWEEK that UAC was indeed susceptible to social engineering attacks. But as Whitehouse said to eWEEK at the time, UAC isnt a security boundary—not a hard one, at any rate. "UAC is not like a firewall, which is a hard security boundary, between your PC and the untrusted Internet," he said. "UAC seems to be more of a security function, but not a boundary. Its useful as a tool to help users but [shouldnt be] seen as impervious." Check out eWEEK.coms Security Center for the latest security news, reviews and analysis. And for insights on security coverage around the Web, take a look at eWEEKs Security Watch blog.
Lisa Vaas is News Editor/Operations for and also serves as editor of the Database topic center. Since 1995, she has also been a Webcast news show anchorperson and a reporter covering the IT industry. She has focused on customer relationship management technology, IT salaries and careers, effects of the H1-B visa on the technology workforce, wireless technology, security, and, most recently, databases and the technologies that touch upon them. Her articles have appeared in eWEEK's print edition, on, and in the startup IT magazine PC Connection. Prior to becoming a journalist, Vaas experienced an array of eye-opening careers, including driving a cab in Boston, photographing cranky babies in shopping malls, selling cameras, typography and computer training. She stopped a hair short of finishing an M.A. in English at the University of Massachusetts in Boston. She earned a B.S. in Communications from Emerson College. She runs two open-mic reading series in Boston and currently keeps bees in her home in Mashpee, Mass.

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