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New IE Zero-Day Attack Bypasses Key Microsoft Security Measures

Microsoft releases temporary browser fix for new flaw being exploited in targeted attacks
Attackers cheated two widely respected Microsoft security features to wage targeted attacks via a previously unknown flaw in Internet Explorer.

Microsoft says the vulnerability resides in IE6, IE7, and IE8 only, and that attacks were waged via IE8. After first issuing an alert on the bug over the weekend, Microsoft then released a temporary workaround that prevents the exploitation of the bug. The software giant is currently working on a patch for the flaw.

Security researchers point to cyberespionage attackers possibly out of China as the culprits in the attacks, which targeted the websites of U.S.-based Council on Foreign Policy, as well as Capstone Turbine Corp. But a new Metasploit module using the bug makes attacks more likely against multiple targets, they say.

"At this point, we are aware of two sites, [and] CFR is one of them. I cannot disclose the other one. It is likely we will see more sites getting infected in the coming hours and days," says Ziv Mador, director of security research at Trustwave. Mador says he can't confirm whether the attack came out of China, but describes it as a "sophisticated" attack that employed "memory-spraying" to work around Microsoft's Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) features aimed at preventing exploitation.

Aside from the drama of a New Year zero-day attack, the exploits highlight yet another APT-type attack employing drive-by website or so-called "watering hole" techniques. This is not your typical spearphishing APT attack, where the attackers use email to go after users associated in some way with the targeted organization in hopes of gaining a foothold in their networks. With this new attack and previous ones seen in 2012, the attackers poison websites where their potential targets frequent, in hopes of infecting them and getting their foot in the door of the targeted organization.

"It is pretty similar to what we have seen in the past, planting an exploit and malware on benign websites," says Jaime Blasco, manager of AlienVault Labs. "If you are able to identify the websites that your desired victims are visiting in a regular basis, you can just put an exploit there and wait until the victim visits the site. On the other hand, you can combine the waterhole campaigns with spearphishing campaigns so you just send a link to the benign Web page within the mail to the victim, and the victim won't notice anything unusual since it is a trusted website."

Waterholing is effective because it can gather multiple targets at once, he says, and it may be an alternative to snaring users who have become more savvy about clicking on links or attachments in emails.

[Cyberespionage attackers more and more are injecting specific, legitimate websites with malware in hopes of snaring victims with common interests -- most recently, human rights organizations. See Cyberspies Target Victims Via 'Strategic' Drive-by Website Attacks.]

Blasco says the vulnerability in IE8 appears to be a "use-after-free" flaw.

Microsoft describes the bug as a remote code-execution vulnerability. It has to do with "the way that Internet Explorer accesses an object in memory that has been deleted or has not been properly allocated. The vulnerability may corrupt memory in a way that could allow an attacker to execute arbitrary code in the context of the current user within Internet Explorer," according to Microsoft's Security Advisory on the bug. "An attacker could host a specially crafted website that is designed to exploit this vulnerability through Internet Explorer and then convince a user to view the website."

Meanwhile, Microsoft is urging users to install the MSHTML Shim Workaround Fix It. "We encourage customers to apply the Fix it, an easy, one-click solution offered with Security Advisory 2794220, to help ensure maximum protection," said Dustin Childs, group manager at Microsoft Trustworthy Computing, in a statement. "Additionally, customers should ensure their anti-malware solution is up-to-date and follow good network hygiene practices, such as enabling a firewall, for added protection against threats."

These types of bugs typically use JavaScript to trigger the flaw, as well as heap-spray to abuse the memory, and bypass DEP and ASLR, according to the software giant.

Microsoft studied the four exploits it has spotted in the attacks, and "they are all very similar," blogged Cristian Craioveanu and Jonathan Ness of Microsoft Security Response Center Engineering.

AlienVault's Blasco says the attackers were likely able to employ some of the DEP and ASLR bypass techniques for Windows 7 that are available online. "On the other hand, I think they spent a reasonable amount of time on the exploit since it contains a working shellcode and ROP chain for different languages, so it requires a good amount of time," he says. Blasco also blogged on his research on the exploit code.

It's unclear thus far whether the attacks are related to the so-called VOHO campaign revealed last fall by RSA Security. The massive targeted cyberespionage campaign has victimized some 900 organizations across various industries, mainly using drive-by Web attacks.

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