botnet

A network of internet connected systems which have been taken over using
security exploits or laughably dreadful password policies. Often older
systems which have not received security updates or which are no longer
supported by the OEM become easy recruits to one or more botnet. Hackers
or government agencies who have remote control over the exploited machines
are known as botmasters. Botnets may be used to carry out DDoS attacks
or a motley assortment of nefarious activities.