The Biba Model is a formal security model focused on maintaining data integrity within a system by preventing unauthorized users from modifying critical information.

Unlike the Bell-LaPadula model, the this model ensures that higher integrity levels are not corrupted by lower integrity levels.

It uses two key rules:

1. The Simple Integrity Property (“no read down”): Subjects at a lower integrity level cannot read data from a higher integrity level, preventing untrusted users from accessing sensitive information.
2. The Star Integrity Property (“no write up”): Subjects at a higher integrity level cannot write data to a lower integrity level, preventing the contamination of critical data by less trusted sources.