The present invention detects a computer virus at high speed from digital data acquired through a network using hardware in virus monitoring. With the invention, in an information processing terminal 002 capable of communicating with other information processing apparatus through a communication network 005, a virus checking apparatus 001 constructed of a hardware circuit is disposed in the side of an input channel of the network 005 and a virus is checked from input data from the network 005 by the virus checking apparatus 001. In order to change a virus pattern collated with the input data by hardware, the hardware circuit is detachably mounted or a rewritable logic device is used in the hardware circuit. The virus pattern of the logic device can be rewritten by sending virus definition information of a server 004 or control data generated based on this information to the virus checking apparatus 001.