September 20, 2012, 11:20 AM — Microsoft on Wednesday released a stopgap defense that protects Internet Explorer (IE) against attacks until the company issues a patch on Friday.
The update will fix five flaws, including one revealed by a security researcher last weekend that hackers have been exploiting to hijack Windows PCs and infect them with malware.
The so-called "zero-day" vulnerability -- meaning it was leveraged by attackers before Microsoft was aware of the bug, much less able to patch it -- has been analyzed and discussed by security experts with increasing intensity since Monday.
Wednesday, for example, U.K.-based Sophos raised its threat level to "high," following moves earlier in the week by rivals like Symantec, which boosted its Internet barometer to "ThreatCon 2."
On Wednesday, Microsoft published a "Fixit" -- one of its automated configuration tools -- that blocks the known exploits. The Fixit has been posted in a support document on Microsoft's website.
The tool is only a temporary measure.
"This Friday, Sept. 21, we will release a cumulative update for Internet Explorer through Windows Update and our other standard distribution channels," said Yunsun Wee, director of Microsoft's Trustworthy Computing Group, in a blog post. "We recommend that you install this update as soon as it is available."
Wee said that the update, tagged as MS12-063, will patch the zero-day bug as well as four other critical vulnerabilities.
Friday's "out-of-band" update will be the first emergency patch that Microsoft has released this year and only the second since September 2010. It will also be the first emergency patch of an IE zero-day vulnerability since one in January 2010 that fixed a flaw exploited by the "Aurora" Trojan horse.