Until now, using passive DNS data for cyber defense was limited by three key factors: timeliness of data, the need to analyze extremely large datasets, and the requirement for expert analysis by traditionally overworked cyber analysts. This Impact Brief shares information on how passive DNS insights can be used as part of a comprehensive cyber defense program, recent developments related to accelerating the availability and analysis of DNS data feeds, and an example of how one organization is using UltraThreat Feeds to rapidly detect and block attacker activities.