A feature of cloud computing in which servers are upgraded or downgraded automatically based on traffic. When traffic spikes for a certain period of time, auto scaling creates a new virtual machine (VM) instance to manage it and disengages the VM when the traffic decreases. The downside of auto scaling is increased server provider fees if the extra traffic ended up being false due to a denial-of-service (DOS) attack. See virtual machine, cloud computing and denial-of-service attack.