Popular Internet Download Manager (IDM) doesn’t update to the new version automatically when available, but it checks for the new release every 2 weeks by requesting an update page from its website. When the update is found, and when you’re not connected to internet or if your Firewall is blocking the update request, then IDM shows’ IDM update notice dialog’ (see the screenshot below).
You can close that dialog, and when your PC is online, permit it to connect to its homepage,fetch and show the update information on your screen.
This is not an annoyance, you don’t need to find a way to disable it unless you’ve registered IDM with fake serial number and trying to block it from updating.
Note: You can always manually check for updates for IDM by selecting the option from the Help menu