Microsoft Disputes PowerPoint Flaw Claim

Microsoft is disputing claims of a zero-day flaw in its PowerPoint application that could allow remote code execution.

“Microsoft’s initial investigation has revealed that this is not a new zero-day vulnerability,” says a Microsoft spokesman. “Microsoft is actively working in conjunction with MSRA partners to verify those findings and will provide additional information and customer guidance once the investigation is complete.”

However, the flaw, whether zero-day or otherwise, appears to be the target of a Trojan.

A 71,168 byte file contains Troj_small.cmz, which is used as a dropper for Troj_mdropper.bh. A randomly named file with an .EXE extension is copied to the Windows Temp folder when the malicious .PPT attachment is opened. The Trojan seeks the location of Temp folder in the following order:

  • C:\Documents and Settings\{current user}\Local Settings\Temp
  • C:\Windows\Temp
  • C:\WINNT\Temp

Folder name ‘Winnt’ is used in older OSs, Windows 2000 and NT4.0.

As of Aug. 21, some AV vendors have reported they have a sample file and they have started an analysis, says Juha-Matti Laurio, a blogger for SecuriTeam and contributor to the Internet Storm Center.

“The specific risk in this case is the fact that Office applications are being installed to almost every company workstation and actually there are not many companies filtering Office file extensions due to their popularity,” says Laurio. “Additionally, there is always a delay when releasing virus signatures against new threats.”

“It is important to be aware of malicious Office files (.PPT, etc.) located on Web pages and shared via instant messengers, etc. too,” adds Laurio. “As mentioned in the FAQ document, many times it is worth calling the sender and asking if he or she sent .ppt attachment that arrived unexpectedly.”

According to Laurio, the flaw is a new vulnerability. As of Aug. 21, Microsoft hadn’t issued a patch and was still investigating the flaw.

The vulnerability is caused by an unknown error when processing malformed PowerPoint documents. Successful exploitation can allow an attacker to run code of choice on the affected machine with the privileges of the most recent logged user.

Vulnerable versions of PowerPoint are running on Windows 95, Windows 98, Windows ME, Windows NT, Windows 2000, Windows XP and Windows 2003 Server systems.

Laurio recommends not opening PowerPoint files from unknown sources sent by e-mail or instant messenger or downloading PowerPoint files from the Web. Updated antivirus signatures may also offer some protection, but you should confirm with your antivirus vendor that it detects this malicious code.

Laurio says that industrial espionage is often the root of cases like this and a zero-day Word issue that happened in May.

News Source: ENT News

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