New Rootkit Targets the Drive's MBR

The bad guys got the idea from Black Hat and a security firm, illustrating the risks of bringing vulnerabilities to light.

Security researchers are warning of a new rootkit/code dropper that has the potential to be a lot nastier if its Russian creators ever get motivated. The rootkit infects the Master Boot Record (MBR) (define) of a computer, where it then installs a Trojan to steal online banking information.

MBR-based attacks have been around since the MS-DOS era. It's a good place to attack because that's the second place a computer checks on startup, after the BIOS (define). Therefore, it has control of the system before the operating system even boots, let alone before any security software is loaded.

This rootkit's existence reflects the inherent risk of shining light on a problem. A proof of concept rootkit that targets the MBR was first proposed by eEye Digital Security in 2005. This concept was then discussed last August at the Black Hat hacker conference in Las Vegas and appeared shortly thereafter.

That's the risk you take when you can't tell the good guys from the bad guys at a show like Black Hat.

"At Black Hat, what people try to do is responsibly disclose potential issues," said Matt Richards, director of the rapid response team for iDefense, which disclosed the rootkit's presence. "They didn't disclose anything ground breaking, they just brought it into the light. Unfortunately, the good guys and the bad guys both saw it."

iDefense first noticed the rootkit in late December. In examining the code, it found it was particularly difficult to remove because of the way it hides in the MBR and the fact that it also hides other Trojans in the MBR.

Infection comes from visiting what seems to be a harmless Web site with a malicious IFrame that links and then tries to exploit several old vulnerabilities in Windows. If there's any consolation, the rootkit only affects Windows XP, not Vista, and the exploits it targets are several months old.

For now, Vista users and those who have kept their computers up to date are safe. Richards said it would be very easy to upgrade the rootkit to be far more dangerous. "It would probably take a few weeks to adapt it to Vista," he said. "The worst case scenario is if they buy a zero-day on the underground and decide to distribute it."

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