https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClGECA0

DNS Security subscription enables users to access real-time protections using advanced predictive analytics. When techniques such as DGA/DNS tunneling detection and machine learning are used, threats hidden within DNS traffic can be proactively identified and shared through an infinitely scalable cloud service. Because the DNS signatures and protections are stored in a cloud-based architecture, you can access the full database of ever-expanding signatures that have been generated using a multitude of data sources. This list of signatures allows you to defend against an array of threats using DNS in real-time against newly generated malicious domains. To combat future threats, updates to the analysis, detection, and prevention capabilities of the DNS Security service will be available through content releases. To access the DNS Security service, you must have a Threat Prevention license and DNS Security license.