There is only one file type that uses the .UMOD extension:
Unreal Tournament Module File
Self-extracting Unreal module installer archive; contains modifications and add-ons for the original Unreal Tournament 3D multiplayer game; includes compressed mod files and a "Manifest.ini" file that defines the locations where the files are to be installed.
NOTE: Unreal 2003 UMOD installers use the .UT2MOD file extension.
Updated: December 26, 2008