WikiLeaks releases source code for a Windows tool that watermarks documents against whistleblowers. Dubbed Scribble, the tool embeds a beacon inside Microsoft Office documents. The CIA uses the tool to track documents that are likely to be copied by insiders, whistleblowers, journalists, leakers, or others. The tool could also be deployed in field operations, as a way to track the activity and location of persons of interest, based on their IP address. Scribble can watermark documents for Office versions 97 to 2016.
Source: https://www.bleepingcomputer.com/news/gaming/wikileaks-publishes-cia-anti-whistleblowers-tool-for-microsoft-office-documents/