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."
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.
ISC warned IE users that more widespread attacks are in the offing. "There is some indication that a weaponized exploit may be in broader circulation now, so expect this to ramp up quickly," the group wrote Saturday. "[And] expect Rapid 7 to likely release Metasploit bits in the near term."
Metasploit is an open-source penetration toolkit maintained by Rapid7, another security company. Metasploit typically rolls out exploit modules for new and even unpatched vulnerabilities. Because Metasploit is a resource for both security professionals and cyber criminals, the appearance of an exploit module often results in increased attacks, as the latter seize on the already-built code to launch their own campaigns.
On Sept. 19 -- last Thursday -- HD Moore, the chief security officer of Rapid7 and the creator of Metasploit, said that no exploit module for the IE bug had yet been added to the toolkit.
If attacks do ramp up, Microsoft would be much more likely to issue an "out-of-band" security update to plug the hole. The next regularly-scheduled Patch Tuesday is more than two weeks away, slated for Oct. 8.
However, out-of-band updates from Microsoft are rare: The last one was MS13-008, an emergency patch issued Jan. 14 that dealt with a vulnerability in IE6, IE7 and IE8 that had been exploited for about six weeks.
Users can also temporarily ditch IE for an alternate browser, such as Google's Chrome or Mozilla's Firefox, to stay safe until Microsoft comes up with a permanent fix.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, or subscribe to Gregg's RSS feed . His email address is email@example.com.