Short version: run the Package Data Report and filter out recognized packages to find un-cataloged software.
Software ID Tags are one of several signature types that BigFix Inventory uses to identify installed software and link it to a catalog entry. Others include finding specific files (by name, size, and/or version), registry entries in Windows and packages in Unix.
The Scanned File Data Report returns a list of files based on standard executable file extensions, such as .sh and .exe., found on all machines that run the File System Scan (which is on by default).
The Package Data Report returns a list of Packages (Unix Package and Windows Registry Uninstall Keys) found on all machines that run the Package Data Scan (which is on by default). Note that the data in this report corresponds with the data you identified in BigFix web reports. Add the filter for
Recognized equal to No to show you what’s not in the Catalog.
I found only one package out of about 2200 in my environment that matched a signature in the catalog, but didn’t have enough information to cause detection of the related software, so you can probably hold off enabling the Caused Detection column (see above). If you decide to enable it, I recommend that you only leave it enabled if there is no significant increase in duration of your data imports.