The Biba Model or Biba Integrity Model developed by Kenneth J. Biba in 1977, is a formal state transition system of computer security policy that describes a set of access control rules designed to ensure data integrity. Data and subjects are grouped into ordered levels of integrity. The model is designed so that subjects may not corrupt objects in a level ranked higher than the subject, or be corrupted by objects from a lower level than the subject.
In general, preservation of data integrity has three goals:
- Prevent data modification by unauthorized parties
- Prevent unauthorized data modification by authorized parties
- Maintain internal and external consistency (i.e. data reflects the real world)
This security model is directed toward data integrity (rather than confidentiality) and is characterized by the phrase: "no read down, no write up". This is in contrast to the Bell-LaPadula model which is characterized by the phrase "no write down, no read up".
In the Biba model, users can only create content at or below their own integrity level (a monk may write a prayer book that can be read by commoners, but not one to be read by a high priest). Conversely, users can only view content at or above their own integrity level (a monk may read a book written by the high priest, but may not read a pamphlet written by a lowly commoner). Another analogy to consider is that of the military chain of command. A General may write orders to a Colonel, who can issue these orders to a Major. In this fashion, the General's original orders are kept intact and the mission of the military is protected (thus, "no read down" integrity). Conversely, a Private can never issue orders to his Sergeant, who may never issue orders to a Lieutenant, also protecting the integrity of the mission ("no write up").
The Biba model defines a set of security rules similar to the Bell-LaPadula model. These rules are the reverse of the Bell-LaPadula rules:
- The Simple Integrity Axiom states that a subject at a given level of integrity must not read an object at a lower integrity level (no read down).
- The * (star) Integrity Axiom states that a subject at a given level of integrity must not write to any object at a higher level of integrity (no write up).
- Multilevel Security - MLS
- Mandatory Access Control - MAC
- Discretionary Access Control - DAC
- Take-Grant Model
- The Clark-Wilson Integrity Model
- Graham-Denning Model
- Security Modes of Operation