The intrusion detection system is just a monitoring system. It sniffs packets of a switch port and logs information or generates alerts. The intrusion prevention system is one step further. It is an active intermediary like a firewall intercepting packet and forwarding them on the network only if it is ok. It blocks attacks in real time and act like an advanced firewall. Most Intrusion prevention systems contain firewall software as well. The latest generation firewalls shares it functionality of deep stateful packet inspection with an intrusion prevention engine to successfully thwart attacks to a system of private network.

Intrusion prevention systems are either host based or network based where the network based intrusion prevention systems has a larger and more modular attack prevention system when compared to a host based system

Content based as well as rate based intrusion prevention systems help in the more modern type of attacks like denial of service or distributed denial of service attacks.

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