DCS includes manifests, which contain hash/size information about core game files. Modules, located in the game install folder are required to have manifests. If case of any manifest check failure, the client is marked as non-IC-compliant and he can't enter servers requiring the IC. Currently, only a selection of files is checked. Sound/texture modifications are not checked yet.
Modules, located in the 'Saved Games' folder are not expected to have manifests, yet.
The big plan is that:
1) the installed game files are not allowed to be modified.
2) all modification to the game can only be done via user-created 'modules'. Be it sound, texture, model, or unit modfication or a mix of such.
3) each user module will be required to have a manifest, created by an official tool (most likely, the tool will be shipped with the game).
This will make the modifications to the game identifiable and controllable - that is, server owners will be able to control which exact versions of user-mods are allowed to be used by their clients.
And of course, all this implies a published documentation on how to use all this features.