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Computerworld - An old, but little-known worm has copied some of the infection strategies of Conficker, the worm that raised a ruckus last week, Microsoft Corp. security researchers said late Friday.

Neeris, which harks back to May 2005, is now exploiting the same Windows bug that Conficker put to good use, and it is spreading through flash drives, another Conficker characteristic, said Ziv Mador and Aaron Putnam, researchers at the Microsoft Malware Protection Center.

According to Mador and Putnam, Neeris' makers recently added an exploit for the MS08-067 vulnerability that Microsoft patched last October. The emergency update -- one of the rare times Microsoft has issued a patch outside its usual monthly schedule --- fixed a flaw in the Windows Server service, which is used for file- and print-sharing by Windows PCs.

Conficker, the worm that began using a new communications scheme to receive commands from its hacker controllers last Wednesday, exploited the same MS08-067 vulnerability to devastating effect in late 2008 and early 2009. In January, for instance, Conficker infected millions of machines, many of them by exploiting MS08-067.

"Neeris [also] spreads via Autorun," Mador and Putnam said in an entry to the malware center's blog. "The new Neeris variant even adds the same 'Open folder to view files' AutoPlay option that Conficker does."

Conficker spread from infected PCs by adding an autorun.inf file to the root directory of any USB-based device, primarily flash drives. Later, when the drive was connected to an uninfected computer, the autorun.inf file silently copied the worm to the machine.

Mador and Putnam speculated that the authors of Conficker and Neeris might be in cahoots. "The earliest samples of Neeris date back to May of 2005, so it seems the Conficker authors may be the copycats here," the argued. "But the Neeris authors added the MS08-067 vector later. Therefore, it is possible that these miscreants somehow collaborate or at least are aware of each other's 'products.'"

Coincidentally, the newest version of Neeris started appearing late on March 31 and on the following day, April 1. The latter date was when Conficker boosted the number of domains it could use to route instructions from its controllers, a deadline that sparked a frenzy of doomsday warnings.

"However, [Neeris] was not downloaded by any Conficker variant, and there's no evidence that it's related to [Conficker.c's] April 1 domain algorithm activation," said Mador and Putnam.

Although Neeris was first identified nearly four years ago, Microsoft has not added a "fingerprint" for the worm to its Malicious Software Removal Tool (MSRT), the antimalware utility that the company updates and redistributes each month to Windows machines. MSRT scans for known malware, then scrubs the system of any it finds. Microsoft added Conficker detection to MSRT in mid-January.

"Due to the similarities to Conficker, most of the mitigations that were mentioned also apply here," said Mador and Putnam. "Make sure to install MS08-067 if you haven't done so yet, and be careful to use only autoplay options you're familiar with, or consider disabling the Autorun altogether."

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