Abstract: A security administration server providing various security services in the LAN and a host server operating in connection thereto are provided. There is installed a security administration server (S) having a function for collecting various log information managed in various devices to be monitored (C) operating in the LAN, a function for generating an image by extracting information useful for security management of the LAN from collected log information and visualizing such information to a form easy for a person to use, and a function for sending the image to another monitoring device (C). Further, the security administration server (S) provides various security services in connection with a host server (H) operating in an external network.