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Despite being superseded by COM, DDE may be enabled in Windows 10 and most of Microsoft Office 2016 via Registry keys.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.
- Understand the behaviour - read the description and the Atomic Tests to see exactly what the attacker does on a host or network.
- Find the telemetry - what data source would reveal it (process creation, registry, network flow, auth logs). Detection Coverage shows which surfaces already have a rule and which are blind.
- Get or write the detection - adapt ready logic (CAR Analytics, SIEM Detections, Falco, or Sigma via Generate a SIEM detection), or author your own.
- Test it - run an Atomic Test in a lab and confirm your rule actually fires. A detection you have not tested is a hope, not coverage.
- Deploy and tune - push it, then watch for false positives and adjust.