Due to internal and external security compliance requiments, a customer need to mask a number...

To mask custom text fields while meeting security compliance requirements and allowing select users to view the field values, a consultant should implement Salesforce ShieldPlatform Encryption (B) and configure profiles accordingly. Shield Platform Encryption provides a higher level of data protection by encrypting sensitive data at rest without compromising application functionality. By configuring profiles, the consultant can specify which users or groups have the permission to view the decrypted field values, ensuring compliance with both internal and external security mandates.References:

https://help.salesforce.com/articleView?id=sf.security_pe_overview.htm

https://help.salesforce.com/articleView?id=sf.pe_profiles_perm_sets.htm