Microsoft Addresses Zero-Day Exploited in Duqu Attacks with ‘Workaround’

Microsoft has released a workaround to address the zero-day bug exploited in the Duqu attacks while it continues to work on a fix.

According to Microsoft, the vulnerability is in the Win32k TrueType font parsing engine. Win32k.sys is a kernel-mode device driver in the kernel of the Windows subsystem. If an attacker were able to successfully exploit this vulnerability, they could potentially install programs and take other actions.

“Today, we released customer guidance and a workaround related to the Duqu malware,” said Jerry Bryant, group manager of response communications for Microsoft Trustworthy Computing, in a statement. “It’s important to note that the associated risk is minimal for the public. Microsoft and our industry partners encourage customers to ensure their antivirus software is up to date, as we continue to work toward a solution for this issue.”

As a workaround, users can deny access to T2EMBED.DLL. Instructions on how to do that are contained in the advisory, linked to here. When the workaround is applied, applications relying on embedded font technology will not display properly.

In a blog post, Bryant added that while the risk to the general public remains low, the company is monitoring the threat landscape and encourages customers to either apply the workaround or ensure their antivirus vendor has protection against the malware.

Microsoft has not said when a fix for the bug – which in the Duqu attacks was exploited via a malicious Microsoft Word file – would be ready. The use of the zero-day was uncovered by the Laboratory of Cryptography and System Security (CrySyS) in Hungary and publicized by Symantec earlier this week. Security vendors have detected victims of Duqu in a number of countries, including Sudan, U.K. and Iran. In October, authorities in India seized components for a server belonging to a company in Mumbai after being told the server was communicating with machines infected with the Trojan.

In addition to the advisory, Microsoft also released its monthly advanced notification for Patch Tuesday today. This month, four bulletins are slated to be released. Of those four, one is rated ‘critical’, one is rated ‘moderate’ and two are considered ‘important.’

The Patch Tuesday bulletins are scheduled to be released Nov. 9 at 1 pm EST.