How to secure it

General approach applicable to many network devices:

• Disable remote access -HTTP, Telnet, FTP.
• Enable authentication for console access.
• Enable SSH access (if required).
• Enable HTTPS access (if required).
• Enable NAT.
• Enable hashing or encryption of secrets in device configuration.
• Change the factory default user accounts and their passwords to strong ones. Online password checkers can be of assistance.
• Use digital certifcates (PKI) instead of user/password authentication.
• Change default SNMP community strings.
• Check manufacturer website for firmware or OS upgrades that address security vulnerabilities and apply.

Knowing the actual device and your situation including expected threats may yield additional suggestions.