Symantec has released a new SONAR Driver update for Symantec Endpoint Protection 12.1 and you want to verify whether you are running the new version.
Symantec Endpoint Protection 12.1 RU1 MP1 and beyond show the updated driver file version in the user interface as SONAR ENGINE version. You can view this from within Symantec Endpoint Protection by going to Help > Troubleshooting > Versions.
In previous versions of Symantec Endpoint Protection 12.1, the SONAR ENGINE field in the same location does not reflect the driver file version accurately. To verify the version of the driver, view the properties of the file BHDrvx86.sys.