METHOD FOR PROTECTION FROM SERVICE-DISABLING ATTACK, SYSTEM FOR PROTECTION FROM SERVICE-DISABLING ATTACK, DEVICE FOR PROTECTION FROM SERVICE-DISABLING ATTACK, RELAY DEVICE, PROGRAM FOR PROTECTION FROM SERVICE-DISABLING ATTACK, AND RELAY DEVICE PROGRAM

摘要

A gate device 8 acquires authorized address information indicating a source address of a non-attacking packet transmitted by an authorized device (address issuing server 10) provided on a network 2. The gate device 8 generates normal condition information indicating conditions for the non-attacking packet based on the authorized address information acquired, and restricts the passage of a packet that attacks on a communication device 7 while allowing the passage of a packet that matches conditions indicated in the normal condition information, among packets received from the network.