(19) United States
(12) Patent Application Publication (io) Pub. No.: US 2001/0052007 Al
Shigezumi (43) Pub. Date: Dec. 13,2001
(54) DNS SERVER FILTER
(75) Inventor: Makiba Shigezumi, Tokyo (JP)
Correspondence Address:
YOUNG & THOMPSON
745 SOUTH 23RD STREET 2ND FLOOR
ARLINGTON, VA 22202
(73) Assignee: NEC Corporation
(21) Appl. No.: 09/750,914
(22) Filed: Jan. 2, 2001
(30) Foreign Application Priority Data
Jan. 21, 2000 (JP) 12757/2000
Publication Classification (51) Int. CI.7 G06F 15/173
(52) U.S. C I 709/223
(57) ABSTRACT
A DNS server filter comprising a packet receiving section for receiving an inquiry from a terminal or a DNS server in a DNS protocol and a response packet from a DNS server, a session management section for managing inquiries and response packets for an entire control having a session management table for managing inquiry requests, a packet verification section for verifying whether the inquiry and the response packet are abnormal, a request generating section for generating an inquiry packet to the DNS server, a response generating section for generating a response packet returned to a transmission source of the inquiry packet, and a packet transmitting section for transmitting the inquiry and the response packet, wherein contents of the received DNS packet are checked that there is no abnormality before the received DNS packet is transmitted to the DNS server and an error response packet is generated and returned to a request source if an abnormality is detected.
