What is it?
An assurance that information remains unaltered from its intended state as it is produced, transmitted, stored, and received. Ensuring integrity may include ensuring the non-repudiation and authenticity of information as well.
Why is it important?
Integrity is considered by many to be the most important element of the confidentiality, integrity, and availability (CIA) security triad. Any system that is otherwise available and confidential can still be rendered useless if a user cannot be confident that the information it contains is trustworthy, accurate, and complete.