Land mine

Land mines are small, passive defense systems that explode when enemies come closer than 2.5 tiles of them, dealing 250 damage and stunning enemies for 3 seconds. Land mines can be placed freely on the map. They deal enough damage to kill small/medium enemies or unarmored players outright, but will only injure and stun larger enemies. Land mines do not damage allied buildings or players. They can be re-built by construction robots after exploding.

After placing, land mines take 2 seconds to arm and bury in the ground. During those 2 seconds, they are visible to enemies and can be destroyed by biters or directly shot by enemy players. After burying, enemy land mines can only be destroyed using weapons with area damage, for example grenades or the flamethrower.

Land mines are the only passive defense in Factorio; if an alien is hit by a land mine, they will not start chasing the player.