What classification includes information that an organization keeps secret?

The classification that includes information an organization keeps secret is 'Confidential.' This designation is used to protect sensitive information that, if disclosed, could potentially harm the organization or its stakeholders. Confidential information often includes trade secrets, internal communications, personnel records, and financial data, which organizations restrict access to in order to safeguard their integrity, competitiveness, and compliance with regulations.

Each of the other classifications has its own connotations: public information is openly accessible to anyone, sensitive data requires protection but may not be entirely secret, and private information pertains to personal data that requires discretion, but not necessarily the same level of secrecy as confidential information. Thus, 'confidential' specifically highlights the need for secrecy and restricted access, making it the most appropriate classification for this context.