Maritime Cargo Security: CBP's Efforts to Address the Impacts of COVID-19, Report to Congressional Committees [open pdf - 2MB]
From the Highlights: "The U.S. economy is dependent on the flow of millions of tons of cargo each day throughout the global supply chain--goods moving from manufacturers to end users. Cargo shipments can present security concerns, as individuals have used cargo containers to smuggle narcotics, stowaways, and other contraband. Within the federal government, CBP [U.S. Customs and Border Protection], a component within the Department of Homeland Security, has responsibility for cargo security. CBP has developed programs that focus resources on identifying U.S.- bound cargo shipments that may be at high risk of transporting terrorist weapons or other contraband and examining those shipments. In addition, CBP provides benefits to CTPAT [Customs Trade Partnership Against Terrorism] members that employ cargo security practices that meet CBP's criteria. Such benefits include expedited processing of their U.S.- bound shipments."
Government Accountability Office: https://www.gao.gov/