Which of the following is the best way to prevent an unauthorized user from plugging a laptop into an employee's phone network port and then using tools to scan for database servers?

MAC filtering is the best option because it restricts network access based on the device's unique Media Access Control (MAC) address. By configuring the network switch to only allow known, authorized MAC addresses, an unauthorized laptop attempting to connect to the port would be denied access, preventing it from scanning for internal resources. Segmentation, while important for network security, divides the network into smaller, isolated segments but doesn't directly prevent an unauthorized device from gaining initial access to a segment if the port is open. Certification refers to digital certificates used for authentication and encryption, not port access control. Isolation typically refers to separating compromised systems or critical assets, which is a reactive measure rather than a proactive prevention of unauthorized access at the port level.