Huawei is being accused of bank fraud and violating sanctions by the US government, which has been pressuring other countries to abstain from using the Chinese company's telecommunications equipment in their networks.
Assistant US Attorney Alex Solomon told the US federal court in Brooklyn that the information in question was obtained under the US Foreign Intelligence Surveillance Act (FISA) and would require classified handling.
This reportedly implies that this information was acquired through espionage.
Huawei has been outspoken in its condemnation of the United States' efforts to push it out of the Western telecommunications industry.