The National Security Agency within the US Department of Defense has announced a programme to mitigate cyber attacks on critical infrastructure such as power plants and the electricity grid.
But the Perfect Citizen programme has raised questions about how it will protect infrastructure owners' independence, according to US reports.
The programme has also raised concerns about what technologies will be used, whether the programme should be public rather than classified, and about privacy protection.
The NSA has denied reports that the programme will monitor communications or place sensors on utility company systems.
The agency has also dismissed suggestions that Perfect Citizen involves invasive or illegal activities and says the programme will follow "both the spirit and letter" of US laws.
The programme reportedly includes a classified $100m contract with defence contractor Raytheon.
The contract provides a set of technical solutions that help the NSA better understand the threats to national security networks, the agency says.