Salted Challenge Response Authentication Mechanism (SCRAM) is the default authentication mechanism for MongoDB.
SCRAM is based on the IETF RFC 5802 standard that defines best practices for the implementation of challenge-response mechanisms for authenticating users with passwords.
MongoDB's implementation of SCRAM provides:
A tunable work factor (the iteration count)
Per-user random salts
Bi-directional authentication between server and client
MongoDB supports the following SCRAM mechanisms:
When you create or update a SCRAM user, you can indicate:
the SCRAM mechanism to use
whether the server or the client digests the password
The minimum driver versions that support
If you use SCRAM-SHA-1: