An access controller not requiring a large amount of resources such as a memory device and not needing to change the list of secure host devices each time the configuration of a network is changed. On receiving a DNS response through an access control section (103) of the access controller (100) a secure host list creating section (104) of the access controller registers the name of the secure host device contained in the DNS response, the IP address, and the IP address of a communication terminal which is a request of the DNS in a secure host list holding section (105) of the access controller (100) when the IP address of the host device contained in the DNS response is the one of the secure host device. The secure host list creating section (104) discards a packet when the communication terminal which is the packet sender is a normal communication terminal and when the packet address is stored in the secure host list holding section (105) and reports nonaccessiblity to the normal communication terminal.