We have the following signature for blocking Internet Download Manager (IDM).
Login to the SonicWALL Mangement GUI.
Navigate to the Firewall > App Control Advanced page. In Gen5 TZ devices this page is under Security Services > App Control
Check the box under Enable App Control and click on the Accept button at the top to enable App Control.
Under App Control Advanced > View Style select DOWNLOAD-APPS under Category;
From the drop-down under Application, select IDM.
Click on Configure.
In the App Control Signature window, select Enable under the Block and Log fields.
Click on OK to save.