Rats

A "rat" is typically an NPC pirate (Serpentis, Dread Guristas, etc.) that passively waits for a player to show up so that they can attack. The lower the security of any given star system, the higher the probability that you will encounter NPC rats in asteroid fields or other specialty locations.

Other issues:

• Rats can also warp into an asteroid field and attack players while they mine.
• NPC rats in mission rooms tend to be rather easy kills in relation to the primary objective of the mission.
• A player rat is someone who hangs out in low-sec space waiting for noobs to warp in so that the player rat can scan them down and then attack if the target represents a non-threat to the player rat.