Microsoft's EMET Security Technology Isn't Impenetrable: Bromium

Bromium demonstrates that Microsoft's Enhanced Mitigation Experience Toolkit has some holes in it.

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Researchers from security firm Bromium today revealed that they have discovered ways to bypass Microsoft's Enhanced Mitigation Experience Toolkit (EMET).

EMET is designed to provide an additional layer of security to applications to reduce the risk of exploitation. While EMET prevents many attacker bullets from getting through to an application, Bromium now asserts that EMET is not bulletproof.

Bromium has been in touch with Microsoft for a few months on the EMET research, and Microsoft peer-reviewed Bromium's research, Rahul Kashyap, chief security architect and head of research at Bromium, told eWEEK.

Bromium's research shows that it is possible to bypass all the protections in EMET, Kashyap said. "By 100 percent bypass, we mean all the protections of EMET were enabled, and we bypassed them," he said.

One focus for Bromium's EMET research was looking at use-after-free memory corruption issues. Use-after-free memory corruption errors are among the most frequently patched flaws across all browser vendors. In a use-after-free memory situation, an attacker can potentially leverage legitimately allocated memory as a base from which to launch an exploit.

The research from isn't just purely theoretical, said Kashyap, adding that the techniques the company discovered to bypass EMET can in fact be turned into a weapon by an attacker. Kashyap noted that in Bromium's research paper, a use-after-free vulnerability in Microsoft's Internet Explorer (IE) Web browser that has already been patched, is leveraged to bypass all EMET protections.

Bromium is not releasing any of the exploit code publicly, Kashyap said.

According to Bromium's research, technologies like EMET that operate on the same plane of execution as potentially malicious code offer little lasting protection. Kashyap explained that what that basically means is that EMET is trying to detect an exploit based on a known exploitation vector. That known exploit vector is typically in the form of a return-oriented programming (ROP) technique used by an attacker. A ROP attack reuses existing code to bypass an operating system's memory protections.

At some point, attackers will come up with newer means of exploitation to bypass defense mechanisms, Kashyap said. "So it becomes a challenge to plug all such exploitation vectors."

EMET isn't the only tool in Microsoft's current arsenal for defending against attacks. There are also the address space layout randomization (ASLR) and Data Execution Prevention (DEP) technologies that are predecessors of EMET. EMET is definitely more advanced than ASLR/DEP, Kashyap said.

"Today, almost all the zero- day malware that we’ve encountered in the wild is able to bypass ASLR/DEP," Kashyap said. "Microsoft has been recommending EMET as the mitigation tool to counter those threats, and it seems to work in most cases."

Even though Bromium has been able to demonstrate that it is possible to bypass EMET, Kashyap stressed that EMET is a good, useful tool.

"We just need to keep on improving it together as a community before the malware authors identify holes," Kashyup said. "In our opinion, Microsoft is taking the right steps to improve their protections. We all just need to continue to keep working together."

Sean Michael Kerner is a senior editor at eWEEK and Follow him on Twitter @TechJournalist.

Sean Michael Kerner

Sean Michael Kerner

Sean Michael Kerner is an Internet consultant, strategist, and contributor to several leading IT business web sites.