According to the CRISC Review Manual1, an acceptable usage policy is a document that defines the rules and guidelines for the appropriate and secure use of IT resources within an organization. It helps to mitigate data leakage risk by establishing the roles and responsibilities of users, the types and purposes of data that can be shared or transmitted, the authorized methods and channels of communication, the security controls and measures to protect data, and the consequences of non-compliance. An acceptable usage policy also educates and raises awareness among users about the potential risks and threats associated with instant messaging and other forms of online communication. Therefore, before implementing instant messaging within an organization using a public solution, an acceptable usage policy should be in place to mitigate data leakage risk. References = CRISC Review Manual1, page 237.