The National Visa Center case number for a U.S. visa application is not technically secret, but it is confidential. Applicants can share visa information, but the U.S. government may not provide visa record information to anyone other than the applicant or a legal representative, states the U.S. Department of State.
To authorize a legal representative for the visa application process, an applicant must submit a completed Form G-28 to the U.S. Citizenship and Immigration Services. The USCIS offers Form G-28 online, and filing the form is free. Only attorneys, accredited representatives and law students with supervision are eligible to serve as a legal representative for the visa application process, states the USCIS.