Swarms are a Threat found when exploring abandoned vessels. The player may be alerted to their presence by a loud fly like 'buzzing' sound. Whenever the swarm is visible, they visibly swarm around a single point constantly, not unlike a nest of angry bees.
This threat is highly dangerous, due to its speed, and ability to deal damage very quickly. Swarms spawn in packs of 20, and move to any point as a group. Additionally, they have the ability to enter vents. When inside of a vent, they make no noise, and may reappear at any other vent on the ship.
Swarms may randomly attack weak closed doors, and will eventually break them down. When a door is attacked, the player is alerted in the console. An attacked door can be opened to prevent it being broken, but the swarm will move into the room blocked by that door. Swarms attacking a door sometimes can be distracted by opening another exit for the swarm and quickly closing it.
The player is not completely helpless against them though. Drones can fire upon swarms with an activated Turret upgrade, at the cost of 20-40 ammo. The drone will not be able dispatch the swarm quickly enough without losing health, due to the speed of the swarm. Another measure the player can use is to open a new room for the swarm to move into, and to close them inside. Listening carefully, a player can know when a swarm has left a room. Like all enemies, they are susceptible to being vented out an airlock.
Swarms have a slightly bigger search radius for stealth drones than leapers and security drones and will detect stealth drones that come too close. While staying in the corner of big rooms with stealth is possible, the player is advised to have a plan B (e.g. sonic or teleport).