Sometimes, heuristic scanners flag indie games as "Unknown." If you trust the source, you may need to add the game folder to your antivirus exclusion list.
Try right-clicking the .exe and selecting "Run as Administrator." SuburbanDemonMother-Version1-pc.zip
Folders containing images, music, and script files (often found in a game/ subdirectory). Sometimes, heuristic scanners flag indie games as "Unknown