Since its discovery a few months ago, the purpose and intention of the Stuxnet worm has remained shrouded in mystery. This Windows based worm is the first ever malware designed to attack industrial equipment.

Specifically it targets Siemens’ Supervisory Control And Data Acquisition (SCADA) software used to control and monitor industrial processes and has the ability to reprogram Siemens’ Simatic PLCs (programmable logic controllers).

PLCs contain code to control automated industrial systems in manufacturing plants or factories. Programmers use the Siemens’ software from a Windows PC to create code and then upload their code to the PLCs. The Stuxnet worm infects the PCs and then uploads its own code to the PLC.

Since the discovery of Stuxnet, conspiracy theories about its purposes have been rampant and these theories have included nation states, well funded hackers, Israeli spies and Iran’s nuclear program. But Symantec have just revealed (http://www.symantec.com/connect/blogs/stuxnet-breakthrough) that the Stuxnet virus only attacks systems with variable-frequency drives from two specific vendors: Vacon based in Finland and Fararo Paya based in Iran. This is sure to reignite the speculations about its target and origin.

What Stuxnet does is monitor the frequency of these drives and only attacks systems that run between 807Hz and 1210Hz which is very high and only used in particular industrial applications. Stuxnet then modifies the output frequency for a short time to 1410Hz and then to 2Hz and then to 1064Hz and thus effects the operation of the connected motors.

Stuxnet’s requirement for particular frequency converter drives and operating characteristics focuses the number of possible speculated targets to a limited set of possibilities.

If you work with PLCs and variable-frequency drives over 807Hz please contact Live Hacking as soon as possible as you might be able to shed some light on this increasingly mysterious malware.