Information SEcurity > Multilevel Security (MLS) > Bell–LaPadula Model

Bell–LaPadula Model: Protecting Confidentiality

Bell–LaPadula Model is a security model designed to protect the confidentiality of information. It is mainly used in Multi-Level Security (MLS) environments such as military and government systems.

In this model, both users (subjects) and files or data (objects) are assigned different security levels such as:

Organizations usually classify information into different security levels:

1. Top Secret - Highly sensitive military or national security information.
2. Secret - Sensitive information such as banking or financial data.
3. Confidential - Business transactions and internal company information.
4. Public - Information available to everyone, such as product lists.

The model controls access using strict security rules.

Main Rules of Bell–LaPadula Model

1. Simple Security Property - “No Read Up”: A user cannot read information at a higher security level than their clearance. Example: A user with “Confidential” clearance cannot read “Secret” files. This rule prevents unauthorized access to sensitive information.
2. Star (*) Property - “No Write Down”: A user cannot write or transfer information to a lower security level. Example: A user working with “Top Secret” data cannot save it into a “Confidential” file. This rule prevents leakage of classified information.
3. Strong Star Property - “No Write Up or Down”: A user can write only at the same security level. This provides even stronger confidentiality protection.

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