Dynamic Data Exchange

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Dynamic Data Exchange
Technique
ID T1173
Tactic Execution
Platform Windows
Permissions Required User
Data Sources API monitoring, DLL monitoring, Process Monitoring, Windows Registry, Windows event logs
Supports Remote No

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 Despite being superseded by COM, DDE may be enabled in Windows 10 and most of Microsoft Office 2016 via Registry keys.123

Adversaries may use DDE to execute arbitrary commands. Microsoft Office documents can be poisoned with DDE commands45, directly or through embedded files6, and used to deliver execution via phishing campaigns or hosted Web content, avoiding the use of Visual Basic for Applications (VBA) macros.7 DDE could also be leveraged by an adversary operating on a compromised machine who does not have direct access to command line execution.

Examples

  • APT28 has delivered JHUHUGIT by executing PowerShell commands through DDE in Word documents. 89
  • APT37 has used Windows DDE for execution of commands and a malicious VBS.10
  • FIN7 spear phishing campaigns have included malicious Word documents with DDE execution.11
  • POWERSTATS can use DDE to execute additional payloads on compromised hosts.12

Mitigation

Registry keys specific to Microsoft Office feature control security can be set to disable automatic DDE/OLE execution.3113 Microsoft also created Registry keys to completely disable DDE execution in Word and Excel.2

Ensure Protected View is enabled14 and consider disabling embedded files in Office programs, such as OneNote, not enrolled in Protected View.613

On Windows 10, enable Attack Surface Reduction (ASR) rules to prevent DDE attacks and spawning of child processes from Office programs.156

Detection

OLE and Office Open XML files can be scanned for ‘DDEAUTO', ‘DDE’, and other strings indicative of DDE execution.16

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.

References