Intrusion Detection and Prevention Systems
When we’re discussing Intrusion Detection Software and Intrusion Prevention Software, we typically combine these two topics into one: Intrusion detection and prevention system (IDPS).
Intrusion detection is the process of monitoring the events occurring in a computer system or network and analyzing them for signs of possible incidents, which are violations or imminent threats of violation of computer security policies, acceptable use policies, or standard security practices. Intrusion prevention is the process of performing intrusion detection and attempting to stop detected possible incidents. Intrusion detection and prevention systems (IDPS) are primarily focused on identifying possible incidents, logging information about them, attempting to stop them, and reporting them to security administrators. In addition, organizations use IDPSs for other purposes, such as identifying problems with security policies, documenting existing threats, and deterring individuals from violating security policies. IDPSs have become a necessary addition to the security infrastructure of nearly every organization.
IDPSs typically record information related to observed events, notify security administrators of important observed events, and produce reports. Many IDPSs can also respond to a detected threat by attempting to prevent it from succeeding. They use several response techniques, which involve the IDPS stopping the attack itself, changing the security environment (e.g., reconfiguring a firewall), or changing the attack’s content.
This tutorial describes the characteristics of IDPS technologies and provides recommendations for designing, implementing, configuring, securing, monitoring, and maintaining them. The types of IDPS technologies are differentiated primarily by the types of events that they monitor and the ways in which they are deployed. This publication discusses the following four types of IDPS technologies:
- Network-Based, which monitors network traffic for particular network segments or devices and analyzes the network and application protocol activity to identify suspicious activity
- Wireless, which monitors wireless network traffic and analyzes it to identify suspicious activity involving the wireless networking protocols themselves
- Network Behavior Analysis (NBA), which examines network traffic to identify threats that generate unusual traffic flows, such as distributed denial of service (DDoS) attacks, certain forms of malware, and policy violations (e.g., a client system providing network services to other systems)
- Host-Based, which monitors the characteristics of a single host and the events occurring within that host for suspicious activity.
Securing IDPS components is very important because IDPSs are often targeted by attackers who want to prevent the IDPSs from detecting attacks or want to gain access to sensitive information in the IDPSs, such as host configurations and known vulnerabilities. IDPSs are composed of several types of components, including sensors or agents, management servers, database servers, user and administrator consoles, and management networks. All components’ operating systems and applications should be kept fully up-to-date, and all software-based IDPS components should be hardened against threats. Specific protective actions of particular importance include creating separate accounts for each IDPS user and administrator, restricting network access to IDPS components, and ensuring that IDPS management communications are protected appropriately, such as encrypting them or transmitting them over a physically or logically separate network. Administrators should maintain the security of the IDPS components on an ongoing basis, including verifying that the components are functioning as desired, monitoring the components for security issues, performing regular vulnerability assessments, responding appropriately to vulnerabilities in the IDPS components, and testing and deploying IDPS updates. Administrators should also back up configuration settings periodically and before applying updates to ensure that existing settings are not inadvertently lost.
Organizations should consider using multiple types of IDPS technologies to achieve more comprehensive and accurate detection and prevention of malicious activity.
The four primary types of IDPS technologies—network-based, wireless, NBA, and host-based—each offer fundamentally different information gathering, logging, detection, and prevention capabilities. Each technology type offers benefits over the others, such as detecting some events that the others cannot and detecting some events with significantly greater accuracy than the other technologies. In many environments, a robust IDPS solution cannot be achieved without using multiple types of IDPS technologies. For most environments, a combination of network-based and host-based IDPS technologies is needed for an effective IDPS solution. Wireless IDPS technologies may also be needed if the organization determines that its wireless networks need additional monitoring or if the organization wants to ensure that rogue wireless networks are not in use in the organization’s facilities. NBA technologies can also be deployed if organizations desire additional detection capabilities for denial of service attacks, worms, and other threats that NBAs are particularly well-suited to detecting. Organizations should consider the different capabilities of each technology type along with other cost-benefit information when selecting IDPS technologies.
Organizations planning to use multiple types of IDPS technologies or multiple products of the same IDPS technology type should consider whether or not the IDPSs should be integrated.
Direct IDPS integration most often occurs when an organization uses multiple IDPS products from a single vendor, by having a single console that can be used to manage and monitor the multiple products. Some products can also mutually share data, which can speed the analysis process and help users to better prioritize threats. A more limited form of direct IDPS integration is having one IDPS product provide data for another IDPS product (but no data sharing in the opposite direction). Indirect IDPS integration is usually performed with security information and event management (SIEM) software, which is designed to import information from various security-related logs and correlate events among them. SIEM software complements IDPS technologies in several ways, including correlating events logged by different technologies, displaying data from many event sources, and providing supporting information from other sources to help users verify the accuracy of IDPS alerts.
Intrusion detection is the process of monitoring the events occurring in a computer system or network and analyzing them for signs of possible incidents, which are violations or imminent threats of violation of computer security policies, acceptable use policies, or standard security practices. Incidents have many causes, such as malware (e.g., worms, spyware), attackers gaining unauthorized access to systems from the Internet, and authorized users of systems who misuse their privileges or attempt to gain additional privileges for which they are not authorized. Although many incidents are malicious in nature, many others are not; for example, a person might mistype the address of a computer and accidentally attempt to connect to a different system without authorization.
An intrusion detection system (IDS) is software that automates the intrusion detection process. An intrusion prevention system (IPS) is software that has all the capabilities of an intrusion detection system and can also attempt to stop possible incidents. This section provides an overview of IDS and IPS technologies as a foundation for the rest of the publication. It first explains how IDS and IPS technologies can be used. Next, it describes the key functions that IDS and IPS technologies perform and the detection methodologies that they use. Finally, it provides an overview of the major classes of IDS and IPS technologies.
IDS and IPS technologies offer many of the same capabilities, and administrators can usually disable prevention features in IPS products, causing them to function as IDSs.
In the next section of this tutorial, we will explore port scanners.