COMMUNICATION SYSTEM AND ADDRESS MANAGEMENT DEVICE, AND ADDRESS MANAGEMENT METHOD AND ADDRESS MANAGEMENT PROGRAM USED FOR THE SAME

摘要

A communication system capable of effectively preventing an attack such as a DoS attack or unauthorized access from a malicious user terminal or an unreliable client and protecting a server from an attack. Upon reception of a predictive notification indicating the possibility of access from the client to the server from a DNS server (3), a traceable ID management server generates a traceable ID which is assigned to each client, adds validity period information to the generated traceable IDs, and returns them to the DNS server. The DNS server (3) provides the traceable IDs to the client as the result of an address solution. Additionally, the traceable ID management server discards the traceable ID assigned to each client upon elapse of the period indicated by the validity period information added to the traceable IDs.