Newly released files show a secret National Security Agency program is targeting the computerized systems that control utilities to discover security vulnerabilities, which can be used to defend the United States or disrupt the infrastructure of other nations.

The NSA's so-called Perfect Citizen program conducts "vulnerability exploration and research" against the computerized controllers that control "large-scale" utilities including power grids and natural gas pipelines, the documents show. The program is scheduled to continue through at least September 2014.

The Perfect Citizen files obtained by the Electronic Privacy Information Center and provided to CNET shed more light on how the agency aims to defend -- and attack -- embedded controllers. The NSA is reported to have developed Stuxnet, which President Obama secretly ordered to be used against Iran's nuclear program, with the help of Israel.