How Secure is Your Network Intrusion Detection System?
A Network Intrusion Detection System (NIDS) offers more than just basic network security.
When implementing a Network Intrusion Detection System (NIDS), there are several different options for connecting it to the network. This CIO how-to article offers advice on secure NIDS configuration.
"Connect the NIDS in front of the firewall (Switch B, purple line). The NIDS sees all hostile activity between the router and the firewall, but cannot see inbound hostile activity blocked by the router or any activity internal to the network at Switch C. The NIDS cannot see what hostile activity leaves the router in the outbound direction and does not know if the router blocks the outbound hostile activity. The NIDS does not know what inbound hostile activity is blocked by the firewall and does not see outbound hostile activity from Switch C that is blocked by the firewall."