.DUN File Extension

Game file created by Dungeon Defenders, a tower defense multiplayer online game; saves information about a player's hero, including experience, items, and other game achievements; saved locally on the iOS or Android device, or on the local desktop computer.

Internet connection settings file used by the Dial-Up Networking (DUN) tool included with some older versions of Windows; saves the phone number and modem settings for connecting to an ISP; often has a corresponding shortcut that is stored on the desktop for quick access.