Siemens: Stuxnet worm hit industrial systems

Siemens confirms that 14 plant systems have been infected; some of them could have been reprogrammed

By , IDG News Service |  Security

A sophisticated worm designed to steal industrial secrets and disrupt operations has infected at least 14 plants, according to Siemens.

Called Stuxnet, the worm was discovered in July when researchers at VirusBlokAda found it on computers in Iran. It is one of the most sophisticated and unusual pieces of malicious software ever created -- the worm leveraged a previously unknown Windows vulnerability (now patched) that allowed it to spread from computer to computer, typically via USB sticks.

The worm, designed to attack Siemens industrial control systems, has not spread widely. However, it has affected a number of Siemens plants, according to company spokesman Simon Wieland. "We detected the virus in the SCADA [supervisory control and data acquisition] systems of 14 plants in operation but without any malfunction of process and production and without any damage," he said in an e-mail message.

This is worrisome news because according to a new paper on the worm, set to be delivered at this month's Virus Bulletin conference in Vancouver, Stuxnet could be used to cause a significant amount of damage if it is not properly removed.

Researchers at Symantec have cracked Stuxnet's cryptographic system, and they say it is the first worm built not only to spy on industrial systems, but also to reprogram them.

Once installed on a PC, Stuxnet uses Siemens' default passwords to seek out and try to gain access to systems that run the WinCC and PCS 7 programs -- so-called PLC (programmable logic controller) programs that are used to manage large-scale industrial systems on factory floors and in military installations and chemical and power plants.

The software operates in two stages following infection, according to Symantec Security Response Supervisor Liam O'Murchu. First it uploads configuration information about the Siemens system to a command-and-control server. Then the attackers are able to pick a target and actually reprogram the way it works. "They decide how they want the PLCs to work for them, and then they send code to the infected machines that will change how the PLCs work," O'Murchu said.

As Wieland noted, there are no known cases of plant operations actually being affected.

However, that's certainly a possibility, according to O'Murchu. Stuxnet comes with a rootkit, deigned to hide any commands it downloads from operators of the Siemens systems. Because of that, Symantec warns that even if the worm's Windows components are removed, the Siemens software might still contain hidden commands. Symantec advises companies that have been infected to thoroughly audit the code on their PLCs or restore the system from a secure backup, in order to be safe.

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