Which network device is intended to act as a security guard, preventing malicious data from accessing your network?

A firewall is a hardware or software solution that acts as a security guard for your network. Firewalls safeguard your network resources in two ways: they protect your network resources from hackers lurking in the dark corners of the Internet, and they can also prohibit computers on your network from accessing unpleasant stuff on the Internet or sending out data that they shouldn't. PoE is an abbreviation for Power over Ethernet, whereas EoP is an abbreviation for Ethernet over Power. Neither has anything to do with security. While a router may include a firewall, it is not a firewall in and of itself. Routers manage communications with other networks or broadcast domains. A firewall can be a standalone physical network appliance or software embedded in another device such as a router.