A user with full permissions and who misuse his powers. Clandestine user: A user who acts as a supervisor and tries to use his privileges so as to avoid being captured.  Types of intrusion detection systems For the purpose of dealing with IT, there are two main types of IDS: Network intrusion detection system (NIDS) It is an independent platform that identifies intrusions by examining network traffic and monitors multiple hosts. Network intrusion detection systems gain access to network traffic by connecting to a network hub, network switch configured for port mirroring, or network tap.
In a NIDS, sensors are located at choke points in the network to be monitored, often in the demilitarized zone (DMZ) or at network borders. Sensors captures all network traffic and analyzes the content of individual packets for malicious traffic. An example of a NIDS is Snort. Host-based intrusion detection system (HIDS) It consists of an agent on a host that identifies intrusions by analyzing system calls, application logs, file-system modifications (binaries, password files, capability databases, Access control lists, etc. ) and other host activities and state.
In a HIDS, sensors usually consist of a software agent. Some application-based IDS are also part of this category. An example of a HIDS is OSSEC. Intrusion detection systems can also be system-specific using custom tools and honeypots. In the case of physical building security, IDS is defined as an alarm system designed to detect unauthorized entry.  Passive and/or reactive systems In a passive system, the intrusion detection system (IDS) sensor detects a potential security breach, logs the information and signals an alert on the console and or owner.
In a reactive system, also known as an intrusion prevention system (IPS), the IPS auto-responds to the suspicious activity by resetting the connection or by reprogramming the firewall to block network traffic from the suspected malicious source. The term IDPS is commonly used where this can happen automatically or at the command of an operator; systems that both “detect” (alert) and/or “prevent. ”  Comparison with firewalls Though they both relate to network security, an intrusion detection system (IDS) differs from a firewall in that a firewall looks outwardly for intrusions in order to stop them from happening.