We have many use cases where we need to copy production data to our lower environments and dynamically mask sensitive fields while maintaining usability .  There is no masking tool built into MongoDB today, and mongoexport could be a good destination to perform this masking and export.  

SQL server has something similar here. https://learn.microsoft.com/en-us/sql/relational-databases/security/dynamic-data-masking?view=sql-server-ver16