Final answer:
The technique where a threat actor moves through the network after penetrating a system is called Lateral Movement.
Step-by-step explanation:
The technique described in the question, where a threat actor penetrates a system and then moves through the network with their elevated position, is called Lateral Movement. Lateral movement involves the attacker gaining further access to different systems and accounts within the network, allowing them to explore and gather information or carry out malicious activities.