Abstract: An intrusion detection system (IDS) detects intruders that is, unexpected, unwanted or unauthorized people or programs on computer network. An IDS is used to determine if a computer network or server has experienced an unauthorized intrusion. An IDS works like a burglar alarm system. If it detects a possible intrusion, the IDS system will send out an alert or warning which would prompt an administrator to perform further investigation which might include computer forensics and prosecution.