The Internet Storm Center on Saturday boosted its threat level to "Yellow," indicating a "significant new threat" to Internet users from attacks exploiting an unpatched vulnerability in all versions of Microsoft's Internet Explorer (IE) browser.
"The Internet Storm Center is beginning to see increased evidence of exploits in the wild regarding Microsoft Security Advisory 2887505," the security organization said on its website. "Accordingly, we're moving the InfoCon up to Yellow."
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Microsoft's advisory, published Sept. 17, acknowledged that hackers were exploiting Internet Explorer 8 (IE8) and IE9, but added that the vulnerability -- which remains unpatched -- affected all versions of the browser, from the 12-year-old IE6 to the not-yet-released IE11. Microsoft has not said when it will patch the bug, but it has offered protective steps customers can take in the meantime.
The Internet Storm Center's (ISC) update to Yellow was triggered in large part by revelations Saturday by FireEye, a Milpitas, Calif. security company. In a detailed analysis, FireEye outlined a hacker campaign that has targeted Japanese organizations since Aug. 19. The campaign uses exploits of the IE "zero-day" vulnerability to compromise Windows PCs and plant additional malware on those machines.
Dubbed "Operation DeputyDog" -- a nod to an animated cartoon character of the early 1960s -- the attack campaign was conducted by the same hacker gang that in February infiltrated the corporate network of Bit9, a Waltham, Mass. security vendor, said FireEye. Once inside Bit9, the cyber criminals issued valid certificates for their own malware, then used those certificates to invade several Bit9 customers' networks.
FireEye first detected the attacks exploiting the unpatched IE bug on Aug. 23, but pointed out that DeputyDog may have started several days earlier, as some payloads were compiled on Aug. 19. If FireEye is correct in its analysis and timeline, the IE vulnerability was in play between three-and-a-half and four weeks before Microsoft notified customers of the threat.
"These attackers have demonstrated previously-unknown zero-day exploits and a robust set of malware payloads," said FireEye of the hackers behind DeputyDog.