Researchers bypass Internet Explorer Protected Mode

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Researchers say they have devised a way to carry out stealthy drive-by exploits even when victims are using recent versions of Internet Explorer with a feature known as Protected Mode.

The attack, described in a paper released by Verizon Business, requires the attacker to have an exploit for a vulnerability that's not currently patched. It works only against machines that have the Local Intranet Zone enabled, as is the default for domain-joined workstations.

Protected Mode, which was introduced in version 7 of IE, is intended to prevent exploit code from accessing sensitive parts of the Windows operating system, such as those that create files or change registry settings. But the Verizon Business researchers said they figured out a reliable way to bypass the measure that requires no interaction on the part of the victim.

“The attack combines the facts that sockets are not subject to Mandatory Integrity Control and that sites in the Local Intranet Zone are rendered with Protected Mode disabled,” the paper states.

“The new malicious web page will be rendered in the Local Intranet Zone and the rendering process will now be executing at medium integrity. By exploiting the same vulnerability a second time, arbitrary code execution can now be achieved as the same user at medium integrity. This provides full access to the user’s account and allows malware to be persisted on the client, something which was not possible from low integrity whilst in Protected Mode.”

A PDF of the paper is here. ®

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