Attacks against unpatched Microsoft bugs multiply

Researchers disagree on attack intensity, but say zero-day ActiveX bug is a big threat

Attacks exploiting the latest Microsoft vulnerability are quickly ramping up in quantity and intensity, several security companies warned today as they rang alarms about the developing threat.

Symantec, Sunbelt Software and SANS' Internet Storm Center (ISC) bumped up their warnings yesterday after Microsoft announced that attackers were exploiting a bug in an ActiveX control used by Internet Explorer (IE) to display Excel spreadsheets. There is no patch for the vulnerability, nor will Microsoft release one later today when it issues its July batch of patches.

A temporary fix that sets the "kill bits" of the ActiveX control is available, but experts believe it's likely most users won't take advantage of the protection.

Symantec raised its ThreatCon ranking to the second of four steps. "We're seeing it exploited, but currently on a limited scale," said Ben Greenbaum, a senior researcher with Symantec security response.

Sunbelt also bumped up its ranking, to high, the company noted today. "We just set the Sunbelt Threat Level to high since our researchers and at least two other major organizations have found in-the-wild exploit code," said Tom Kelchner, malware researcher with the Florida-based firm.

Meanwhile, the ISC went to condition Yellow after discovering numerous sites hosting attack code. The ISC reported both broad and targeted attacks using exploit code against the new zero-day. "[There was] a highly-targeted attack against an organization earlier today who received a Microsoft Office document with embedded HTML," said the ISC in a frequently-updated blog post. "This one was particularly nasty.... It was specifically crafted for the target, with the document being tailored with appropriate contact information and subject matter that were specific to the targeted recipient."

Broader attacks are originating from compromised sites in China, the ISC added. "A .cn domain [is] using a heavily obfuscated version of the exploit, which may become an attack kit (think MPACK), and is similar to recent DirectShow attacks," said the center.

Last week, Microsoft confirmed that hackers were exploiting an unpatched bug in an ActiveX control that's part of DirectShow, a component of the DirectX graphics platform within Windows.

McAfee echoed the ISC late on Monday, confirming that attack code targeting yesterday's ActiveX bug has been added to a Web exploit toolkit and is being distributed from hijacked Chinese sites. The toolkit also contained attack code for last week's DirectShow vulnerability. Some computers in Spain, the U.K. and Germany also showed evidence of compromises, McAfee researcher Haowei Ren said in an entry to the company's security blog.

Symantec's Greenbaum added that while his company is seeing only a small number of attacks currently -- "It's not in the top 500 attacks," he said -- this has the potential to get big, and big quickly. "It's the kind of attack that can be very easily hosted on a Web server, and meets all the criteria for large-scale attacks in the relatively near future," Greenbaum said.

The number and diversity of attacks will likely increase because working exploit code is publicly available, he said.

Although Microsoft is working on a patch for the new vulnerability, it's unclear when it will be ready. Users will definitely not receive any automatic protection today, however. "Unfortunately, the comprehensive update for this vulnerability is not quite ready for broad distribution," a company spokesman said yesterday afternoon. "We recommend that customers follow the automatic 'Fix It' workaround ... to help secure their environment against this vulnerability while we finish up development and testing of the comprehensive update."

Fix It requires users to manually steer their browser to Microsoft's support site and download, install and run the tool to disable the ActiveX control.

That means many users won't be protected. "Most users won't [manually] mitigate," agreed Greenbaum.

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Gregg Keizer

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