Turns out the big patch Microsoft issued for Internet Explorer yesterday covered not just one zero-day attack, but another that had been under way for at least a month.

This second zero-day attack exploited a "use-after free" flaw (CVE-2013-3897) and was patched yesterday along with the memory corruption vulnerability that Microsoft had temporarily plugged with an emergency Fix It last month.

Security researchers at Websense, Symantec, and SpiderLabs all are investigating the malware and attacks, which appear to focus specifically on targets in South Korea and Japan. The attacks date back as far as Aug. 23, according to Websense, and are focused on heavy industries and financial firms.

"It was just targeting XP machines and very specific, looking for Japanese and Korean language packs," says Alex Watson, director of security research at Websense. Watson says it's not unusual for targeted attacks on heavy industries to also include attacks on financial firms that might have information on those high-technology and manufacturing companies.

The attacks have all the earmarks of Chinese cyberespionage campaign, he says.

SpiderLabs, meanwhile, in a blog post yesterday said the attacks appear to have begun in the first half of September 2013, and have Japanese and Korean XP users in the bull's eye. But the researchers say the attackers are trying to steal user credentials from online gaming applications.

"In short, this payload is responsible for a number of malicious activities. It attempts to disable any security products that may be running on the victim machine, redirects banking sites to a malicious IP address, and tries to steal credentials for popular online games," says Daniel Chechik, a SpiderLabs researcher. "The various techniques used indicate that this payload is not meant for any targeted scenario, but instead will simply try to target any Korean or Japanese users it stumbles upon."

Websense's Watson says while half of the targeted machines Websense spotted in the attack were in the U.S., those appear to be inadvertent, collateral damage. "Those industries and targets didn't match what the exploit is looking for," he says.

[A new model of cyberespionage is emerging that relies on cybermercenaries hired to break in, steal information, and then leave -- with specific targeted information. See Rise Of The 'Hit-And-Run' APT.]

Microsoft's blanket patch for 10 flaws across multiple versions of IE -- version 6 through 11 -- supersedes the Fix It tool it issued for the IE 8 and IE 9 zero-day attacks (CVE-2013-3893), where an attacker could spread the malware via a drive-by download.

"In my opinion, [the blanket IE update] is a sign of really good software engineering practices," Watson says. "They are making sure that they maintain as much of the common code base across all versions as possible."

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