Patent ID: 7013343
Filing Date: 2006-03-14
Classification: H04L

Abstract:
1. A DNS server filter apparatus comprising: packet verification means for verifying whether there is any abnormality in contents of a received DNS (domain name system) packet before transmitting it to a DNS server and for verifying whether there is any abnormality in contents of a to-be-transmitted DNS packet before transmitting it from the DNS server; and error response means for generating an error response packet and transmitting it to a request source if an abnormality is detected, wherein said packet verification means checks the received DNS packet for obtaining information on a host name, a domain name, and an IP (Internet protocol) address transmitted from a network outside an organization by a person outside the organization using a DNS protocol; and wherein said error response means generates an error response packet and transmits it to a request source when detecting an abnormality, thereby preventing the person outside the organization from invading a network of the organization by using private information of the organization and preventing the DNS server from operating abnormally by receiving a packet having an abnormal format, and wherein said packet verification means checks the to-be-transmitted DNS packet for obtaining information on a host name, a domain name, and an IP address transmitted to a DNS server belonging to a network outside the organization by a person inside the organization using a DNS protocol, and wherein said error response means generates an error response packet and transmits it to the request source when detecting an abnormality, thereby preventing the person inside the organization from invading the network outside the organization.