Electrical Instrumentation

Virus on PLC's?

Virus on PLC's?


Yes, they do already exist…


Stuxnet is a virus discovered in June 2010. It was designed to attack Siemens Step7 software running on a Windows operating system. Not the PLC model we use in our class (S7-1200) but one very similar, the Siemens S7-300.  





Stuxnet does little harm to computers and networks that do not meet specific configuration requirements; 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.  It only attacks PLC systems with variable-frequency drives from two specific vendors: Vacon and Fararo Paya. Furthermore, it monitors the frequency of the attached motors, and only attacks systems that spin between 807 Hz and 1210 Hz. The industrial applications of motors with these parameters are diverse…




So, what was the purpose?


It is believed that Stuxnet almost ruined one-fifth of the Iranian nuclear centrifuge by spinning out of control while simultaneously replaying the recorded system values which shows the normal functioning centrifuge during the attack. The worm worked by first causing an infected Iranian IR-1 centrifuge to increase from its normal operating speed of 1,064 hertz to 1,410 hertz for 15 minutes before returning to its normal frequency. Twenty-seven days later, the worm went back into action, slowing the infected centrifuges down to a few hundred hertz for a full 50 minutes. The stresses from the excessive, then slower, speeds caused the aluminum centrifugal tubes to expand, often forcing parts of the centrifuges into sufficient contact with each other to destroy the machine!




Fortunately you are not learning to do this on our PLC units but PLC programming is truly interesting and has a wide range of applications…


If you want to learn more about Stuxnet go to http://en.wikipedia.org/wiki/Stuxnet.




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A fair dinkum wager you’d be hard pressed to lose


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