If an attacker changes the IP to MAC address mapping on a computer, what type of attack has occurred?

The situation described involves an attacker manipulating the mapping of IP addresses to MAC addresses on a network. This type of attack is known as ARP poisoning, which specifically targets the Address Resolution Protocol (ARP). ARP is used to resolve IP addresses to MAC addresses so that devices on a local network can communicate effectively.

In ARP poisoning, the attacker sends out forged ARP messages onto the network. These messages can falsely associate the attacker's MAC address with the IP address of another device, such as a default gateway or another host. As a result, traffic meant for the legitimate device is redirected to the attacker's device, allowing for various malicious activities such as data interception, man-in-the-middle attacks, or session hijacking.

Understanding ARP poisoning is crucial in network security, as it highlights vulnerabilities in local area networks and emphasizes the need for protective measures such as static ARP entries or the use of dynamic ARP inspection when possible.