According to Dr. Sloan, Fortnite scanners is the only way to receive a warning about the alien movement. These devices can obviously track alien, even with their stealth technology, but you must visit various alien areas on the island to install them.

To keep a close eye on the movement of the aliens and what they are going to do next, this is where the Fortnite scanner needs to be deployed in the alien biome.

Fortnite scanners in the Alien Biome locations
Source: Epic Games

There are 7 Alien Biome location where Fortnite scanners are to be deployed, each located in a different purple biome area.

  1. W of Boney Burbs near Flopper Pond
  2. S of Pleasant Park near Red Steel Bridge
  3. E of Pleasant Park near Grumpy Gravel
  4. NW of Corny Complex near Scenic Spot
  5. SE of Boney Burbs near The Aftermath
  6. S of Corny Complex opposite to Gas N’ Grub
  7. S of Steamy Stacks opposite to Compact Cars

That is all for where the scanners are needed to be deployed to fight those aliens.