A threat is any potential danger to an asset. If a vulnerability exists but has not yet been exploited-or, more importantly, it is not yet publicly known-the threat is latent and not yet realized.

Explanation
An ARP-based MITM attack is achieved when an attacker poisons the ARP cache of two devices with the MAC address of the attacker's network interface card (NIC). Once the ARP caches have been successfully poisoned, each victim device sends all its packets to the attacker when communicating to the other device and puts the attacker in the middle of the communications path between the two victim devices. It allows an attacker to easily monitor all communication between victim devices. The intent is to intercept and view the information being passed between the two victim devices and potentially introduce sessions and traffic between the two victim devices