There is disclosed an information processing system which makes it impossible for a malicious third person to intrude thereinto from the outside through an external network for altering information recorded on a storage device of the server system or surreptitiously reading mails in the mailbox. This information processing system comprises a writable storage device (21), first and second input/output channels (18 and 19) connected to the storage device (21), a first computer (22) connected to the first input/output channel (18) and a second computer (23) connected to the second input/output channel (19). The first computer (22) is connected to an external network (24) such as the Internet and an intranet. The first input/output channel (18) is arranged as a channel exclusively for performing reading from the storage device (21) or a channel exclusively for performing writing into an empty area of the storage device (21) in dependence on the application of this information processing system. The first input/output channel (18) and the second input/output channel (19) are driven independently of each other. The information processing system in which the first input/output channel (18) is a channel exclusively for reading from the storage device (21) is suitable for the maintenance and/or management of a home page. The information processing system in which the first input/output channel (18) is a channel exclusively for performing writing into the storage device (21) is suitable for the maintenance and/or management of e-mails.