What is the primary action a company should take to improve the security of a network switch that was breached using default credentials?

Changing the default credentials of the switch is the primary action a company should take to improve the security of a network switch that was breached using those credentials. Default credentials are often widely known and readily available to potential attackers, making devices vulnerable to unauthorized access. By changing these credentials to strong, unique passwords, the company significantly strengthens the security posture of the switch. This action directly addresses the root cause of the breach, reducing the risk of future unauthorized access.

While options like implementing network segmentation, increasing bandwidth, or installing firewall measures can enhance overall network security, they do not specifically mitigate the immediate vulnerability associated with the use of default credentials on the switch. Without addressing the credential issue first, any additional security measures may still leave the switch exposed to further attacks. Therefore, altering the default settings is a critical first step in securing the network environment.