Contrary to what some forums say, this is a virus. It is IDM’s built-in defense mechanism. Even if you uninstall and reinstall the program, the "fake" flag often stays hidden in your Windows Registry.

Before you search for another "crack" or "patch" (which likely caused this in the first place), let’s talk about what this message actually means and how to remove it for good.

IDM Keep Saying "Fake Serial Number"? Here’s the Real Fix (No Hacks)