Symantec has shed more light on potential vulnerabilities in Windows Vista that could circumvent new security measures and leave users vulnerable to attack.

The security specialist expects hackers will try to work around restrictions in Windows Vista that sandbox code downloaded from the internet in the hopes of preventing attacks on other PC system resources. Symantec says it's just a matter of time before "a low-privilege, low-integrity level process" will ultimately bypass Windows Vista's new system for securing user's machines "and ultimately execute code at a high- privilege, high-integrity level."

Symantec released the information in its latest paper, Analysis of the Windows Vista Security Model Analysis, which updates its overview of Windows Vista's network security last month. Readers wanting technical details should click here for the PDF.

The paper stresses its assessment is based on an out-of-the box installation of Windows Vista running on code used in Microsoft's February Community Technology Preview (CTP). Symantec concedes later builds of the operating system have closed potential gaps, and that Windows Vista's out-of-the-box security is already a "significant" improvement over previous versions of Windows.

However, Symantec's principal security researcher Matthew Conover wrote he "expects several other privilege escalation vulnerabilities to be discovered."

The nub of the issue appears to be a system of privileges Windows Vista assigns to both code and the end user. Microsoft's User Account Control (UAC) asks users to enter their credentials, which will depend on their company's security policy, before they are allowed to do things like install software.

Windows Vista also defines the "integrity" of things like objects and processes to control different levels of access they have to different system resources.

According to Microsoft's documentation, all files and registry keys will have a "medium" default integrity level, while IE running in protected mode - which it will do when installed out of the box - has a "low" integrity level. That means IE is not allowed to modify existing files on a Windows Vista machine, and will receive "access denied" error messages should it try to change files.

One popular means of attacking PCs is for the user to either visit a web site running malicious code, with code automatically downloading, installing and consuming system resources or stealing data. Another is for the user to download and install code, breezing through any warning pop-ups that get in way. Changes in Windows Vista are designed to close these avenues of attack.

Conover, though, expects hackers will see this defense strategy as a potential challenge. He expects hackers will look for ways to turn code downloaded using IE from low to medium or even high integrity. Next, he predicted it will be "just a matter of time" before hackers find ways to abuse Windows local and remote procedure calls (LPCs and RPCs) using high-integrity processes.

LCPs and RPCs a favored method of attacking servers and PCs running older versions of Windows.

Of course, hyping Vista security fears can't hurt Symantec's business.®

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