The United States customs logistics data is sourced from the USA Customs, Border Protection and similar agencies from other countries, and obtained through the FOIA (Freedom of Information Act), while data from other countries is legally obtained proprietary data and database.
Customs data by country or by company contains import information from the Bill of Lading data for shipments entering or leaving countries. For the U.S., you can buy this shipping manifest data for shipments entering the country by ocean from the U.S. Department of Homeland Security.