Based on how the IDS is set-up and configured, and the type of Intrusion Detection System being used, the system works by trying to understand the normal process or data flow in and out of a company’s computer network and tries to assess the ‘normal behavior” of the said flow. Once this is accomplished, it can then spot out any anomalous behavior or abnormal behavior which usually occurs when there is a log of suspicious activity, breach of the computer system, data theft, or any other form of attack.
Intrusion Detection Systems usually have sensors: a console that can help monitor events and an engine that records and stores the event data into set databases following certain rules and generates alerts when these rules are not met.
An IDS (and its various types -- active Intrusion systems or Passive Intrusion detection systems), hence, can help protect the company’s computer systems, data and network from misuse, theft or any sort of compromise. It can also be used to audit the networking systems, run routine checks and keep the business processes uninterrupted.