Hello Najam
Ill start with clarifying what these baseline are and what's their purpose with an example.
Lets say we have created a new database, we have added 3 users with some roles in the database, we have configured some firewall rules on the resource firewall of the SQL.
These will all be considered a vurnabillity since they are not part of your "baseline". What happens when you use the "add to baseline" is that Defender will save the current configuration (their are different baselines for firewall and user roles, but the idee is the same). Once this configuration is saved you will be compliant again with this in Defender.
The purpose of this is to ensure you have control over these setting, if someone add a new user/new firewall rule (after you added your current configuration to baseline), this new configuration will no longer match your baseline and it will show you what rule is not in baseline. Now you can easily evaluate if the new rule is correct, and if it is just add it to baseline.
Why it works like this is since Defender cant really know if a firewall rule or a User role is correctly configure, but it wants to you to be completely aware of these configurations and make a decision about them and also notify you when something is changed :)
Hope this is helpful,
Best Regards,
Timmy Malmgren
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