Which of the following actions is NOT advisable for securing devices in a datacenter?

Maintaining default passwords is not advisable for securing devices in a datacenter because default passwords are often widely known or easily accessible to potential attackers. Many devices come with preset passwords that are documented in manuals or online resources, making it simple for an unauthorized user to gain access. Once an attacker knows a device's default password, they can potentially compromise the entire system, creating vulnerabilities that could lead to data breaches or service disruptions.

In contrast, regular updates and patching help protect devices from newly discovered vulnerabilities. Closing unused ports reduces the attack surface by limiting access points that malicious actors could exploit. Restricting guest access further enhances security by ensuring only authorized personnel can access sensitive systems and data, thereby reducing the risk of unauthorized access and potential threats.