Patent ID: 8479282

Claim:
A system for protecting a communication device against a denial-of-service attack, the system comprising: a monitoring device provided on a local area network including the communication device, the monitoring device being configured to monitor a packet transmitted to the communication device via an internet-service-provider network; and a restricting device provided on the internet-service-provider network, the restricting device being configured to restrict a packet to the local area network, wherein the monitoring device includes an attack detecting unit configured to detect an attack by the packet on the communication device based on an attack detection condition including a destination address and a port number of the packet, and a protection-request-information transmitting unit configured to transmit to the restricting device protection request information indicating a request for protection against the attack, the protection request information including a certificate authenticating the monitoring device, a signature indicating a feature including the destination address and the port number of a packet that attacks the communication device, the protection-request-information transmitting unit being configured to update the protection request information to remove packets not included in the attack from restriction based on a report of received packets transmitted from the restricting device, and the restricting device includes a packet restricting unit configured to restrict a packet transmitted to the communication device via the internet-service-provider network based on the protection request information.