Autons, also known as Nestene Drones, are creatures of living plastic created and controlled by a foul entity called the Nestene Consciousness. They come in many different forms - since an Auton can be anything that is made of plastic - but the most common form of Auton footsoldier is a common shop window dummy, or mannequin. They are brought to life by Nestene signals and edited on a molecular level, giving them weapons and senses. Nestenes are also capable of creating realistic replicas of Humans out of plastic, and they use this to their advantage in their nefarious infiltration attempts.
Though they are often thwarted by the Doctor, the Autons rarely give up, and they are constantly on the lookout for more sources of power. They have also allied themselves with the Master several time, but he has often betrayed them. Due to the Autons resilence most races avoid conflict with them, and they are one of the few member races of the League who do not follow its orders entirely. They joined the Legaue for trade - nothing more.
Many people also believe that the Autons are active in every corner of the Galaxy and are simply dormant, waiting for the right moment to strike. Anti-Nestene signals protect League planets from infiltration, but these have been shown to be ineffective at best.