Dorkbot’s Java weapon hit 3.5m PCs in 30 days

Microsoft continues its campaign on un-patched Java.

Image credit: Microsoft.

The recent spike in the Skype-spreading Dorkbot malware was accelerated by an exploit that “guaranteed” infecting any platform running un-patched Java.

Since April 2011, Microsoft has detected Dorkbot 28 million times, however an exploit for a serious Java flaw that Oracle released a patch for in late August hit 3.5 million Windows machines throughout the month after October 15, according to Microsoft’s telemetry data.

The exploit for CVE-2012-4681 was “guaranteed to work” for vulnerable Java Runtime Environments and could just as easily infect computers running Windows, Mac OS X or Linux, Microsoft notes in an analysis of the malware.

Prior to the patch, the flaw was being used in targeted attacks associated with the Poison Ivy trojan thought to be a tool of Chinese hackers. After Oracle's patch it became used in mass malware campaigns such as Dorkbot, but also others, in the hope of netting victims that had not applied Oracle's patch.

An outbreak of the password stealing Dorkbot occurred this October after it began spreading over Skype and MSN Messenger instant messages. However, that method of infection tricked victims in to clicking on links and installing the malware.

The Java exploit allowed Dorkbot’s controllers to automatically infect victims via drive by download, so long as they had not updated to the Java version.

Microsoft last week warned that another surge in Java-based malware attacks could emerge in coming months after researchers identified several widely-used online crime kits that had bundled a similarly potent Java exploit for a vulnerability Oracle patched in October.

"To avoid getting infected through drive-by downloads, make sure your software is up to date – for Java specifically," said Horea Coroiu of Microsoft’s Malware Protection Centre in Munich.

"Always make sure your definitions are up-to-date for your antivirus solution. If you don't have one and you're running Windows XP, Vista, or 7, you can download and install Microsoft Security Essentials for free. If you're using Windows 8, make sure your antivirus program is enabled and running properly."

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