A second Trojan used in the latest zero-day attack against Microsoft Office contains characteristics that pinpoint corporate espionage as the main motive, according to virus hunters tracking the threat.

According to an alert from Symantec (SYMC), a backdoor called Trojan.Riler.F is installing itself as a layered service provider, or LSP, allowing it access to every piece of data entering and leaving the infected computer.

An LSP is a legitimate system driver linked deep into the networking services of Windows. It is used primarily to allow the operating system to connect to other computers, but virus writers have found a way to make malicious programs work as LSPs to hijack sensitive data during transmission.

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Symantec, of Cupertino, Calif., said the Trojan also opens a back door on the compromised system and connects to the "soswxyz.8800.org" domain. The Trojan then listens and waits for commands from a remote attacker.

Alfred Huger, senior director of engineering at Symantec, said the dirty PowerPoint file infects the machine with a piece of malware called Trojan.PPDropper.C which in turn drops two separate backdoors that give the attack unauthorized access to the compromised computer.

The first Trojan, called Backdoor.Bifrose.E, logs keyboard strokes, hijacks sensitive system data and transmit the information back to a remote server hosted in China.

F-Secure, an anti-virus vendor with headquarters in Finland, said the Bifrose backdoor file is an uncompressed PE executable that is encrypted with a simple algorithm. The backdoor is programmed to connect to "pukumalon.8800.org," which is a free host bouncing service in China.

The 8800.org domain, like other similar hosting services, has been used in several zero-day attacks this year, according to F-Secure researcher Mikko Hypponen.

The F-Secure anti-virus team found backdoors connecting to China-hosted domains in March 2005, September 2005, March 2006, April 2006, May 2006 and July 2006.

"If you're not in China and your users are not supposed to access different Chinese services, blocking might not break too many things," Hypponen said.

"We'd recommend you at least check your company's gateway logs to see what kind of traffic you have to such services," he added.

Microsoft declined a request for an interview to discuss the characteristics of the attacks and referred queries to the company's PowerPoint security advisory.

Symantec's Huger said the sophisticated nature of the attacks suggest it is the work or well-organized criminals associated with industrial espionage.

"It's difficult to say if all the Office attacks we've seen this year are related to each other but they are using very similar techniques that are very sophisticated," Huger said in an interview with eWEEK.

In both the Excel and PowerPoint attacks, for example, there is a never-before-seen attempt to hide forensic evidence.

"Whether it's the same attacker, we don't know. But this is not a technique we've seen before. Instead of leaving a dirty file, the author is overwriting it with a clean file. That's a new level of sophistication," Huger said.

He confirmed Microsoft's claim that the attacks were "very limited" but warned against businesses in the United States becoming complacent.

"Once this type of attack is out, it's very unusual for it to be limited to just one company. I think it's safe to assume that it's ongoing, especially since there is no patch for this vulnerability," Huger added.

Microsoft plans to issue a patch on August 8 for users of Microsoft PowerPoint 2000, Microsoft PowerPoint 2002 and Microsoft PowerPoint 2003.

In the meantime, anti-virus experts are urging Microsoft Office users to be on the lookout for suspicious attachments, even those that appear to come from colleagues internally.

The PowerPoint exploit arrives from a Gmail address with a subject line in Chinese characters.

Internet security vendor Sophos said the rigged PowerPoint presentation, which includes 18 slides, contains "humorous" philosophy about love between men and women.

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