Which type of exploit normally requires the culprit to have prior access to the target system?

A local exploit is executed on the target system itself, meaning the attacker must already possess initial access, such as a user account, before they can use the exploit to escalate privileges or perform further malicious actions within that system.

Denial of service (DoS) attacks aim to make a service unavailable and typically do not require prior access to the target system for the initial attack vector.

A system vulnerability is a flaw in the system that can be exploited, not the exploit itself, and doesn't inherently define the access requirement.

A remote exploit is executed over a network against a target system without requiring prior direct access to that system.