Dynamic Data Exchange
Windows Dynamic Data Exchange (DDE) is a client-server protocol for one-time and/or continuous inter-process communication (IPC) between applications. Once a link is established, applications can autonomously exchange transactions consisting of strings, warm data links (notifications when a data item changes), hot data links (duplications of changes to a data item), and requests for command execution.
Object Linking and Embedding (OLE), or the ability to link data between documents, was originally implemented through DDE. Despite being superseded by COM, DDE may be enabled in Windows 10 and most of Microsoft Office 2016 via Registry keys.   
Adversaries may use DDE to execute arbitrary commands. Microsoft Office documents can be poisoned with DDE commands  , directly or through embedded files , and used to deliver execution via phishing campaigns or hosted Web content, avoiding the use of Visual Basic for Applications (VBA) macros.  DDE could also be leveraged by an adversary operating on a compromised machine who does not have direct access to command line execution.
Registry keys specific to Microsoft Office feature control security can be set to disable automatic DDE/OLE execution.    Microsoft also created, and enabled by default, Registry keys to completely disable DDE execution in Word and Excel. 
OLE and Office Open XML files can be scanned for ‘DDEAUTO', ‘DDE’, and other strings indicative of DDE execution. 
Monitor for Microsoft Office applications loading DLLs and other modules not typically associated with the application.
Monitor for spawning of unusual processes (such as cmd.exe) from Microsoft Office applications.
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