Most of the what we know about the Stuxnet worm, which some consider the most sophisticated malware ever, has come from independent security researchers. They noted it could attack the Siemens industrial systems that control power plants, oil pipelines and the like. And they also pointed out that a disproportionate number Iranian computers were infected. Taking those facts together, speculation ran rampant that some state-backed entity created the worm to hamper Iran's nuclear push.
Now, various Iranian agencies have acknowledged the worm's presence, even though (as you might expect) they provided little detail about particular targets or defenses. The Mehr News Agency ran a story with headline, "Iran Successfully Battling Cyber Attack."
One interesting thing to note is that Mehr described the worm as "designed to transfer data about production lines from our industrial plants to (locations) outside of the country." International security researchers went quite a bit farther, noting that what made Stuxnet special was its ability to control industrial systems, not just snoop on them.
The Bushehr nuclear power plant project manager denied that Stuxnet had any impact on the "main systems of the Bushehr power plant," on Iran's Arabic-language Al-Alam television network."All computer programmes in the plant are working normally and have not crashed due to Stuxnet," the manager said.