In the fields of
physical security
Physical security describes security measures that are designed to deny unauthorized access to facilities, equipment, and resources and to protect personnel and property from damage or harm (such as espionage, theft, or terrorist attacks). Physi ...
and
information security
Information security is the practice of protecting information by mitigating information risks. It is part of information risk management. It typically involves preventing or reducing the probability of unauthorized or inappropriate access to data ...
, the high-water mark for
access control
In physical security and information security, access control (AC) is the action of deciding whether a subject should be granted or denied access to an object (for example, a place or a resource). The act of ''accessing'' may mean consuming ...
was introduced by
Clark Weissman in 1969. It pre-dates the
Bell–LaPadula security model, whose first volume appeared in 1972.
Under high-water mark, any object less than the user's security level can be opened, but the object is relabeled to reflect the highest security level currently open, hence the name.
The practical effect of the high-water mark was a gradual movement of all objects towards the highest security level in the system. If user A is writing a CONFIDENTIAL document, and checks the unclassified dictionary, the dictionary becomes CONFIDENTIAL. Then, when user B is writing a SECRET report and checks the spelling of a word, the dictionary becomes SECRET. Finally, if user C is assigned to assemble the daily intelligence briefing at the TOP SECRET level, reference to the dictionary makes the dictionary TOP SECRET, too.
Low-water mark
Low-water mark is an extension to
Biba Model. In the Biba model, no-write-up and no-read-down rules are enforced. In this model, the rules are exactly opposite of the rules in
Bell-La Padula model. In the low-water mark model, read down is permitted, but the subject label, after reading, will be degraded to object label. It can be classified in floating label security models.
See also
*
Watermark (data synchronization) A Watermark for data synchronization describes an object of a predefined format which provides a point of reference value for two systems/datasets attempting to establish delta/incremental data synchronization, synchronization; any object in the que ...
References
Computer security models
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