Information
The use of dictation is likely to include editing documents with confidential information. While Apple does have controls to obfuscate voice data that exists on their servers it is recommended that Dictation collected information does not leave the local Mac.
Rationale:
Sending data from dictation to the Siri servers could allow data spillage to occur. From a control perspective it is much safer to ensure information of various levels of confidential is retained locally.
Impact:
Keeping all dictation on-device does not allow the system to better understand and learn, through machine learning, from the user.
Solution
Graphical Method:
Perform the following steps to ensure the firewall is enabled:
Open System Settings
Select Keyboard
Set Dictation to your organization's requirements