Countdown to Zero Day: Stuxnet and the Launch of the World's First Digital Weapon

by Kim Zetter

Before Stuxnet began its assault on the S7-315 PLC, it made sure the system was using frequency converters made by Vacon and Fararo Paya, and that the converters were operating at a frequency somewhere between 807 Hz and 1,210 Hz. Stuxnet was looking for a plant that had up to 186 of the converters installed, all of them operating above 800 Hz. Frequency converters were used in a number of varied applications, but converters that operated at 600 Hz or higher had limited use—so limited, in fact, that when Chien did a search online he discovered they were regulated for export in the United States by the Nuclear Regulatory Commission. There could be no doubt about it now. Stuxnet was targeting a nuclear facility. Langner had gone out on a limb asserting that Stuxnet was targeting Iran’s nuclear program, but now they had evidence in the code to back it up.