There are 10 different types of Anomaly Class ranging from Class 1 (easiest) to Class 10 (hardest).
Class 1=(Faction) Hideaway or Drone Cluster (easiest)
Class 2=(Faction) Burrow or Drone Collection
Class 3=(Faction) Refuge or Drone Gathering
Class 4=(Faction) Den or Drone Assembly
Class 5=(Faction) Yard or Drone Surveillance
Class 6=(Faction) Rally Point or Drone Menagerie
Class 7=(Faction) Port or Drone Herd
Class 8=(Faction) Hub or Drone Squad
Class 9=(Faction) Haven or Drone Patrol
Class 10=(Faction) Sanctum or Drone Horde (hardest)