Network-Based IDS (NIDS)

From Computing and Software Wiki

As opposed to monitoring the activities that take place on a particular network, Network-based intrusion detection analyzes data packets that travel over the actual network. These packets are examined and sometimes compared with empirical data to verify their nature: malicious or benign. Because they are responsible for monitoring a network, rather than a single host, Network-based intrusion detection systems (NIDS) tend to be more distributed than host-based IDS. Software, or appliance hardware in some cases, resides in one or more systems connected to a network, and is used to analyze data such as network packets. Instead of analyzing information that originates and resides on a computer, network-based IDS uses techniques like “packet-sniffing” to pull data from TCP/IP or other protocol packets traveling along the network. This surveillance of the connections between computers makes network-based IDS great at detecting access attempts from outside the trusted network. In general, network-based systems are best at detecting the following activities:

   * Unauthorized outsider access: When an unauthorized user logs in successfully, or attempts to log in, they are best tracked with host-based IDS. However, detecting the unauthorized user before their log on attempt is best accomplished with network-based IDS.
   * Bandwidth theft/denial of service: These attacks from outside the network single out network resources for abuse or overload. The packets that initiate/carry these attacks can best be noticed with use of network-based IDS.

Some possible downsides to network-based IDS include encrypted packet payloads and high-speed networks, both of which inhibit the effectiveness of packet interception and deter packet interpretation. Examples of network-based IDS include Shadow, Snort!, Dragon, NFR, RealSecure, and NetProwler.