Virtual Threat Contributing Writer
Stuxnet worm was discovered in June 2010. It initially spreads via Microsoft Windows, and targets Siemens industrial software and equipment. While it is not the first time that hackers have targeted industrial systems, it is the first discovered malware that spies on and subverts industrial systems, and the first to include a programmable logic controller (PLC) rootkit.
The worm initially spreads indiscriminately, but includes a highly specialized malware payload that is designed to target only Siemens supervisory control and data acquisition (SCADA) systems that are configured to control and monitor specific industrial processes. Stuxnet infects PLCs by subverting the Step-7 software application that is used to reprogram these devices.
This video demonstrates how W32.Stuxnet can compromise a Programmable Logic Controller (PLC), resulting in unintended consequences for the machines connected to it. From the Symantec Security Response blog.
Different variants of Stuxnet targeted five Iranian organizations, with the probable target widely suspected to be uranium enrichment infrastructure in Iran; Symantec noted in August 2010 that 60% of the infected computers worldwide were in Iran. Siemens stated on 29 November that the worm has not caused any damage to its customers, but the Iran nuclear program, which uses embargoed Siemens equipment procured secretly, has been damaged by Stuxnet. Kaspersky Lab concluded that the sophisticated attack could only have been conducted “with nation-state support”. This was further supported by the F-Secure’s chief researcher Mikko Hyppönen who commented in a Stuxnet FAQ, “That’s what it would look like, yes”. It has been speculated that Israel and the United States may have been involved.
In May 2011, the PBS program Need To Know cited a statement by Gary Samore, White House Coordinator for Arms Control and Weapons of Mass Destruction, in which he said, “we’re glad they [the Iranians] are having trouble with their centrifuge machine and that we – the US and its allies – are doing everything we can to make sure that we complicate matters for them”, offering “winking acknowledgement” of US involvement in Stuxnet. According to Daily Telegraph, a showreel that was played at a retirement party for the head of the Israel Defence Forces (IDF), Gabi Ashkenazi, included references to Stuxnet as one of his operational successes as the IDF chief of staff.
Unlike most malware, Stuxnet does little harm to computers and networks that do not meet specific configuration requirements; “The attackers took great care to make sure that only their designated targets were hit…It was a marksman’s job. While the worm is promiscuous, it makes itself inert if Siemens software is not found on infected computers, and contains safeguards to prevent each infected computer from spreading the worm to more than three others, and to erase itself on 24 June 2012.
For its targets, Stuxnet contains, among other things, code for a man-in-the-middle attack that fakes industrial process control sensor signals so an infected system does not shut down due to abnormal behavior. Such complexity is very unusual for malware. The worm consists of a layered attack against three different systems:
- The Windows operating system,
- Siemens PCS 7, WinCC and STEP7 industrial software applications that run on Windows and
- One or more Siemens S7 PLCs.
Experts believe that Stuxnet required the largest and costliest development effort in malware history. Its many capabilities would have required a team of people to program, in-depth knowledge of industrial processes, and an interest in attacking industrial infrastructure. Eric Byres, who has years of experience maintaining and troubleshooting Siemens systems, told Wired that writing the code would have taken many man-months, if not years. Symantec estimates that the group developing Stuxnet would have consisted of anywhere from five to thirty people, and would have taken six months to prepare. The Guardian, the BBC and The New York Times all claimed that (unnamed) experts studying Stuxnet believe the complexity of the code indicates that only a nation-state would have the capabilities to produce it. The self-destruct and other safeguards within the code imply that a Western government was responsible, with lawyers evaluating the worm’s ramifications. Software security expert
(sources: Wikipedia and Youtube)