Disclosed are a system and method of sharing intrusion detection information detected at different networks and tracking the intrusion, to thereby defense against the intrusion on a network to which an intruder belongs, and a computer-readable medium storing a program for implementing the above method therein. The system detects an intrusion through the analysis of an input packet, adds information associated with the intrusion into the packet, creates an active packet and transmits the active packet to an address of an intruder, which transmitted the packet. Thereafter, the system tracks the intrusion, for all routes through which the intruder passed based on the active packet, and filters the packet associated with the intruder for the isolation thereof.