Tag Archives: vista

ATI Driver Flaw Exposes Vista Kernel to Attack

Security researchers have discovered a flaw with an ATI driver that allows unsigned and potentially dangerous code to be installed and loaded into the Vista kernel.

In order to increase security and to protect against attack, Microsoft have introduced a new driver signing requirement in Vista. By requiring that drivers are signed, Microsoft hoped that this would ensure that only drivers which were verified as being clean and compatible with Vista could be installed.

ATI duly had their drivers signed by VeriSign so that they could be installed on a Windows Vista system. Unfortunately, their was a flaw in one of the drivers. Apparently the flaw was originally intended as a shortcut in the driver that allowed ATI developers to load modules into the driver for testing. When the driver was released, either no-one thought to remove the shortcut or ATI forgot about it.

In order to close the hole, ATI will have to patch the flaw in their driver, have it signed with a new certificate, roll-out the update via Windows Update, then have the original signing authority revoke the original certificate. It’s not a straightforward process and it’s by no means foolproof either.

Program Names Matter on Windows Vista

One of the selling points of Windows Vista is it’s increased security. User Account Control, (UAC), is designed to ensure that unknown programs aren’t launched without the users express permission. The idea is sound, but the actual implementation may be off.

The Register reports that the name of the program has a major bearing on whether or not UAC asks the user to authenticate the installation. If the program is named “install.exe” for example, then Vista will require that the program have admin rights and UAC will prompt the user to cancel or allow installation. However, if the program name does not contain any references to “install”, “update” or “uninstall” then Vista will happily let it run without user intervention, even though it is the exact same program.

Microsoft responded that Vista was designed to automatically detect install, update and uninstall programs. As these types of programs generally need to write to protected areas of the registry and system files, then Vista would prompt for admin rights to be assigned to the program.

While Vista may have been designed to detect these type of programs, it seems that all it is doing is checking the program name, otherwise renaming the program would not allow the program to run without UAC prompting the user. While this type of behaviour may offer a modicum of protection, it can be sidestepped by using an innocuous file name. The big question now is how long will it take for malware authors to use this to bypass UAC and get their programs on to a Vista machine?