While IP addresses are often dynamically assigned during runtime, hardware addresses (so called MAC addresses) are usually statically allotted when a network interface card is manufactured. What happens when an attacker connects to the same network as his target and assigns his network card the same MAC address as the one of his target’s system?
I understand this is called MAC spoofing. Since routers cannot tell to which port the correct system is attached, packets will likely be routed to both devices. An attacker can thus gain access to sensitive information.
How would a user or a sender come to know that an attacker has gained access to sensitive information?
I understand that MAC filtering provides absolutely zero security (Wired networks).