Changing the default credentials of a new device is critical to securing it from unauthorized access, as default usernames and passwords are often well-known and easily guessable, making devices with unchanged credentials an easy target for attackers. Updating the device's firmware is important, but it would still be susceptible to attack if the default credentials are left unchanged. While monitoring network traffic and conducting regular security audits are important security practices, they would not prevent an attacker from exploiting default credentials.