Stallings, W., & Brown, L. (2017). Computer Security: Principles and Practice. Pearson Education.
Covers access control, information flow, and covert channels.

Anderson, R. (2020). Security Engineering: A Guide to Building Dependable Distributed Systems. John Wiley & Sons.
Explains multilevel security and covert channel risks.

Pfleeger, C. P., Pfleeger, S. L., & Margulies, J. (2015). Security in Computing. Prentice Hall.
Discusses trusted systems and covert channel concepts.

NIST Special Publication 800-53 (Rev. 5): Security and Privacy Controls (Control SC-31: Covert Channel Analysis)
https://csrc.nist.gov/publications/detail/sp/800-53/rev-5/final
Provides standard guidelines for covert channel analysis and mitigation.

Covert Channel Overview — Wikipedia
Gives a fundamental overview of covert channels and information leakage.