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IE, Chrome Browser Attack Exploits Windows PCs

Microsoft says the social-engineering vulnerability, which uses "pop-under" browser notifications and a fake Captcha, isn't a Windows bug.
Might Microsoft issue a patch to lock down the Windows user interface and block these types of attacks? In fact, Microsoft has issued a statement saying that it doesn't see the related Windows behavior as constituting a vulnerability. It also said that browser security tools, such as the Smart Screen filter first introduced with IE8, will help block related exploits.

"We are aware of this industry-wide social engineering technique that requires user interaction to run a malicious application," according to Microsoft's statement. "This is not a vulnerability, as someone must be convinced to visit a malicious site and take additional action, such as using a keyboard shortcut to execute the malicious application. Smart Screen will help mitigate the risk for customers running Internet Explorer. We continue to encourage customers [to] exercise caution when visiting untrusted websites."

But Valotta said Microsoft's Smart Screen technology isn't infallible. "There are a lot of ways to circumvent Smart Screen," he said. One technique would be to use a stolen extended validation signing certificate to give the malware a good reputation. Another technique is to use extweets -- shortened URLs made to link to malicious executables -- of which Valotta said about 20% don't appear to be on Microsoft's list of bad code, or classified as malware by Virus Total.

Microsoft Windows User Access Control (UAC) settings can also help block attacks that target the notification-mechanism vulnerabilities, for example by flashing a warning -- above all other windows -- whenever an application requests administrator privileges. But Valotta said that admin-level access isn't required to do damage, and cites malware such as Carberp that's able to inject JavaScript and HTML into the client browser to make it appear to be a legitimate site.

How might Microsoft or Google lock down Windows or their respective browsers to block these types of attacks? Valotta offered several recommendations, including altering browsers so that any notifications tied to background windows be brought to the front after a preset period of delay, as well as disabling use of the tab key in notification windows and ensuring that all important notifications -- for example, file-download alerts -- are displayed in a static browser frame that can't be hidden in a pop-under window.

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