What are the four levels of data classification for government information?

The four US government classification levels from highest to lowest sensitivity are top secret, secret, confidential, and unclassified. Top secret information could cause exceptionally grave damage to national security if disclosed. Secret information could cause serious damage. Confidential information could cause damage. Unclassified information requires no protection from disclosure. Private sector organizations typically use different labels such as confidential, private, sensitive, and public.