Final answer:
ARP (Address Resolution Protocol) is the least likely to be part of a session hijacking or spoofing attack.
Step-by-step explanation:
ARP (Address Resolution Protocol) is the least likely to be part of a session hijacking or spoofing attack. The ARP protocol is used to map an IP address to a physical MAC address on a local network. It is not typically involved in session communication, making it less vulnerable to attacks compared to UDP, TCP, and HTTP protocols.