No matter how secure any system is, we need to keep a close eye on the system from an auditing perspective to make sure that we detect possible breaches and stop them as soon as possible.
This feature is available only for MongoDB Enterprise Edition.
For users of the Community Edition version, we have to set up auditing manually by logging changes to documents and collections in the application layer, possibly in a different database altogether. This will be addressed in the next chapter, which covers advanced querying using client drivers.