Hidden in the closed doors of a nondescript red brick and gray building of the Idaho National Laboratory is the malware laboratory where paid government cyber experts conducted test in the Stuxnet computer virus.

The malicious software targets extensively used industrial control systems created by German firm Siemens. Cyber experts believe that it first appeared and aimed mostly at Iran’s nuclear program and that its sophistication denotes that are coming from a nation state, possibly the United States or Israel.