Apache Ranger provides security to deliver monitor, manage data security to Hadoop clusters.
It provides a centralized platform define, administer & manage security policies in Hadoop.
If a policy doesn’t exist in Ranger, then Ranger would default to native permissions model in HDFS (POSIX or HDFS ACL)
The option for fallback model is configured using a property in Ambari > Ranger > HDFS config > Advanced ranger-hdfs-security xa.secure.add-hadoop-authorization