Stuxnet scored quick hit on first target, says researcher

Infected Iranian PC just 12 hours after worm's code was compiled, reports Symantec

Stuxnet infected its first target just 12 hours after hackers finished the worm, an indication that the malware scored an almost instant bulls-eye, a researcher said today.

The makers of Stuxnet launched the worm "as soon as they had it ready," Liam O Murchu, manager of operations of Symantec's security response team, said in an interview Monday.

"They knew where they wanted to deliver it, and to whom, and because that domain was targeted several different times, it shows they really wanted to get into [that target]," O Murchu added.

On Friday, Symantec published new information on Stuxnet, the worm that most suspect was aimed at Iran's nuclear program, including the uranium enrichment centrifuges at its underground Natanz facility.

In its newest Stuxnet analysis, Symantec said that 10 original infections in three waves over an 11-month period had targeted five domains linked to organizations within Iran. Symantec has declined to name the organizations, saying only that all five were involved in industrial processing.

As the worm spread, those 10 infected PCs later hijacked about 12,000 Iranian computers.

Symantec also compared each worm variant's compile time- and date-stamp -- when the attackers finished work on the malicious code -- with each version's first infection to track the speed with which Stuxnet did its damage.

It took the initial variant, compiled on June 22, 2009, just 12 hours to infect its first PC, said O Murchu, one of three Symantec experts who have spent months digging into the worm's code. The short interval means that the attackers planned carefully, he said, and had pinpointed their targets long before they had wrapped up their work.

Other targets in the first wave were infected six days, 14 days and 26 days after the worm code was compiled.

Previously, Symantec has said that one target of Stuxnet was the Natanz facility, where Iran houses thousands of high-speed centrifuges that can be used to enrich uranium into bomb-grade material. Within Stuxnet is code crafted to grab control of the high-speed electrical motors that spin centrifuges. According to Symantec, Stuxnet sabotages those centrifuges by speeding up and slowing down their motors.

Iranian officials have confirmed that the worm infected tens of thousands of the country's PCs, and have admitted that Stuxnet affected the operation of some of the centrifuges used to enrich uranium. The country has blamed Israel and the U.S. for the attacks.

Last month the New York Times, citing confidential sources, said that the worm was a joint American-Israeli project, and had been tested on Iranian-style centrifuges at the latter's secret nuclear facility at Dimona.

The average time between compilation and infection for all 10 initial attacks was 19 days, and the median was 26 days, said Symantec.

Another target in the first wave was also the most important, said O Murchu, who noted that the organization was hit not only in mid-2009, but also by two later waves in March and April 2010. That organization was the only one of the five infected by all three attacks.

Of the three waves of Stuxnet attacks -- June 2009, March 2010 and April 2010 -- the second was the most successful, according to O Murchu.

The March 2010 variant was the first to include an exploit of a vulnerability in how Windows parsed shortcut files, the small files displayed by icons on the desktop, on the toolbar and in the Start menu that launch applications and documents when clicked. By crafting malicious shortcuts, the hackers could automatically execute malware whenever a user viewed the shortcut or the contents of a folder containing the malevolent shortcut.

"That exploit was far more effective than the original AutoRun attack," said O Murchu, referring to the June 2009 Stuxnet's reliance on malformed files contained on a USB drive. "[Using the Windows shortcut vulnerability] allowed [the March 2010] Stuxnet to spread so much faster."

Stuxnet was able to exploit the shortcut bug for months before the vulnerability went public in June 2010. Microsoft rushed an emergency patch to customers in early August.

Although there were only minor differences between the March 2010 and April 2010 variants, the former infected more machines, and had a better chance of reaching the intended target, said O Murchu. He was at a loss to explain the difference, but speculated that the first PC infected by the March wave may have been better connected to other Iranian computer networks.

Most analysts have assumed that the initial attacks were delivered on infected USB drives since it would be unlikely that Natanz is directly connected to the Internet. O Murchu said it was impossible to tell from the Stuxnet code if that was the case, however.

"It could have been delivered on a USB drive, but whether it was, or as an e-mail attachment, we can't tell," he said.

Symantec's revised report on Stuxnet can be downloaded from the company's site (download PDF).

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer or subscribe to Gregg's RSS feed . His e-mail address is

Copyright © 2011 IDG Communications, Inc.

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