High-water mark (computer security)
（重定向自Low watermark）
High-water mark was introduced in Clark Weissmann 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.