RangerIDS - Intrusion Detection System (IDS)
The final approach is to forget about trying to identify the attacks directly, and concentrate instead on ignoring everything that is considered “normal”. This is known as “anomaly-based” IDS, and the basic principle is that, having identified what could be considered “normal” traffic on a network, then anything that falls outside those bounds could be considered an “intrusion” – or at the very least, something worthy of note.
The primary strength of anomaly detection is its ability to recognise previously unseen attacks, since it is no longer concerned with knowing what an attack looks like – merely with knowing what does not constitute normal traffic. Its drawbacks, of course, include the necessity of training the system to separate noise from natural changes in normal network traffic (the installation of a new – perfectly legitimate - application somewhere on the network, for example).
Changes in standard operations may cause false alarms while intrusive activities that appear to be normal may cause missed detections. It is also difficult for these systems to name types of attacks, and this technology has a long way to go before it could be considered ready for “prime time”.