Patent ID: 8406396

Claim:
A communication system that shares terminal identification information used for identifying a terminal that sends a spam phone call, with another communication system belonging to another network provider, the system comprising: a storage section that stores terminal identification information of a terminal that sends a spam phone call; a transmission section that transmits the terminal identification information stored in the storage section to the other communication system; a reception section that receives, from the other communication system, the terminal identification information used for identifying the terminal that sends the spam phone call; a registration section that registers the terminal identification information received by the reception section in the storage section; a spam phone call determination section that determines whether or not there is a match between terminal information indicating information of an outgoing call terminal that sends a connection request, and the terminal identification information stored in the storage section, thereby determining whether or not the outgoing call terminal sends a spam phone call; and the communication system further comprising: a hashing section that hashes the terminal information and the terminal identification information using a hash function common to the other communication system, wherein the reception section receives the terminal identification information hashed by the common hash function, and the spam phone call determination section determines whether or not there is a match between the terminal information of the outgoing call terminal that is hashed by the hashing section and the hashed terminal identification information stored in the storage section, thereby determining whether or not the outgoing call terminal sends a spam phone call.