How To hide secret data / Files inside MS Word files structures

Newer office suite (2007 – 2010 – 2013) are built using the open XML file format, this format consists of a zip file that contains many XML and binary files and has the DOCX extension, if we unzip this file we can have a folder named with the same file name and contains three folders and one XML file in the main directory named [Content_Types].xml.

Figure 1: Content of Word document (2007 and later version) after unzipping it

Open [Content_Types].xml and add this line to the end of the file before the </Types> tag:

<Override PartName=”/HiddenProgram.exe” ContentType=”HiddenProgram.exe”/>

Where HiddenProgram.exe is the name of the program or file that we want to hide inside the Word file (it could be any file type), now we need to put our hidden program in the main directory and Zip the folder again and rename its extension to DOCX, this method encapsulate our Word document with another file/program hidden inside it.