What evidence suggested that Stuxnet targeted Iran’s nuclear program?

Evidence that Stuxnet targeted Iran’s nuclear program was identified by computer security experts through the worm's highly specific technical requirements and geographic distribution.1

Key indicators included:

• Targeted Hardware: The malware was designed to infect Siemens AG SCADA systems used with specific frequency-converter drives programmed to operate industrial motors at precise high speeds.1
• Geographic Concentration: By the end of 2010, over 60 percent of the approximately 100,000 infected computers were located in Iran.1
• Operational Anomalies: The worm’s circulation coincided with reports from the Naṭanz uranium-enrichment plant, where an unusually high number of centrifuges—which require high-speed rotation—were taken out of service and replaced.1

These factors led analysts to conclude that the cyber attack was aimed at disrupting Iranian nuclear installations, such as the enrichment facility at Naṭanz or the nuclear reactor at Būshehr.1