The Bell-LaPadula model is a security framework designed to protect sensitive information in computer systems. It focuses on maintaining data confidentiality by enforcing access controls based on security levels. Users can only access information at their own security level or lower, preventing unauthorized access to classified data. The model operates on two main principles: the simple security property, which prohibits users from reading data at a higher security level, and the star property, which prevents users from writing data to a lower security level. These rules help ensure that sensitive information remains secure from unauthorized disclosure.