Denial-of-service-attack protecting method, denial-of-service attack protecting system, denial-of-service attack protecting device, repeater, denial-of-service attack protecting program, and program for repeater

摘要

A gate device acquires authorized address information indicating a source address of a non-attacking packet transmitted by an authorized device, i.e., an address issuing server, provided on a network. The gate device generates normal condition information indicating conditions for the non-attacking packet based on the authorized address information acquired, and does not allow passage of an attacking packet while allowing passage of a non-attacking packet. The non-attacking packet is one that satisfies the conditions indicated in the normal condition information.