We can assure you that our game client doesn't contain a virus. Double-check that you are receiving the game from our distributors. If the game came from our website, then this is a false positive from the Anti-virus software.
Antivirus companies get to choose what they white list and what they don't. If a file isn't white listed you typically can choose to download it and use it anyway by manually allowing it.
You will need to look through the settings for your antivirus to create an exception to be able to run omdu.exe.