Full administrative control means an attacker has the highest level of privileges on a device, usually the same power a legitimate administrator would have. They can change settings, create or remove accounts, alter logs, install code, and control services or network paths.
In cyber security, this is more serious than a simple login compromise because it turns a vulnerable system into attacker-owned infrastructure. On routers, servers, and other management-plane devices, full control can let an intruder redirect traffic, open remote access, weaken defenses, or persist by adding scheduled tasks and scripts. Defenders treat this outcome as a high-severity incident because patching the original flaw may not remove the attacker’s changes. After exposure, administrators should review accounts, configuration, startup items, and logging for signs of unauthorized control.