This document discusses how metadata, hidden information, and lost data can be extracted from files using tools like FOCA for tactical fingerprinting purposes. It provides examples of the types of information that can be found, such as users, paths, devices, and more. The document warns that most people and organizations are unaware of these issues and fail to properly clean files before publishing them. It demonstrates how tools can extract this extra information and identifies weaknesses in common file types and cleaning procedures. The author encourages thorough cleaning of documents and limiting what users publish to avoid unintentionally leaking sensitive information.