Distributed Checksum Clearinghouse (DCC) is a hash sharing method of spam email detection. Which of the following protocols does the DCC use?

TCP is not used by DCC; the protocol intentionally uses UDP to avoid the connection overhead and latency that TCP's handshake would introduce during high-frequency hash queries.

TELNET is a remote terminal access protocol and plays no role in DCC's hash-sharing spam detection mechanism.

ICMP is a network diagnostic and error-reporting protocol and is not used for DCC client-server hash exchange communication.

DCC clients communicate with DCC servers over UDP, making it lightweight and efficient for the high-volume, low-latency hash lookups required for real-time spam detection. The DCC protocol was specifically designed around UDP to minimize connection overhead when querying distributed checksum databases at scale.