Additional security statement updates

Author: srowen

docs/quick-start.md

@@ -32,11 +32,6 @@ you can download a package for any version of Hadoop.
 
 Note that, before Spark 2.0, the main programming interface of Spark was the Resilient Distributed Dataset (RDD). After Spark 2.0, RDDs are replaced by Dataset, which is strongly-typed like an RDD, but with richer optimizations under the hood. The RDD interface is still supported, and you can get a more detailed reference at the [RDD programming guide](rdd-programming-guide.html). However, we highly recommend you to switch to use Dataset, which has better performance than RDD. See the [SQL programming guide](sql-programming-guide.html) to get more information about Dataset.
 
-# Security
-
-Security in Spark is OFF by default. This could mean you are vulnerable to attack by default.
-Please see [Spark Security](security.html) before running Spark.
-
 # Interactive Analysis with the Spark Shell
 
 ## Basics

docs/security.md

@@ -23,7 +23,10 @@ license: |
 
 # Spark Security: Things You Need To Know
 
-Security in Spark is OFF by default. This could mean you are vulnerable to attack by default.
+Security features like authentication are not enabled by default. When deploying a cluster that is open to the internet
+or an untrusted network, it's important to secure access to the cluster to prevent unauthorized applications
+from running on the cluster.
+
 Spark supports multiple deployments types and each one supports different levels of security. Not
 all deployment types will be secure in all environments and none are secure by default. Be
 sure to evaluate your environment, what Spark supports, and take the appropriate measure to secure