The signer distinguished name (SDN) is required when you enable a digital signature check and exclude only files signed by a specified process signer.
Task
Select Menu → Reporting → Threat Event Log.
Click the Adaptive Threat Protection event (Adaptive Threat Protection prefix in the Action Taken field) to display details.
Select and copy the Source Process Signer details.
When creating exclusions, paste the Source Process Signer details as a single line of text to the Signed by field.
For example, the SDN required format is:
C=US, S=CALIFORNIA, L=MOUNTAIN VIEW, O=MOZILLA CORPORATION, OU=RELEASE ENGINEERING, CN=MOZILLA CORPORATION