What Is an Intrusion Prevention System (IPS)?

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An Intrusion Prevention System (IPS) is a security technology designed to detect and actively block or mitigate unauthorized access, malicious activities, and potential threats within a computer network or system. It is a crucial component of any network security strategy that works with other security solutions to provide comprehensive identification and protection against threats.

Also known as an Intrusion Detection and Prevention System (IDPS), Intrusion Prevention Systems are considered extensions of Intrusion Detection Systems (IDS) because they both monitor network traffic and/or system activities for malicious activity. The main difference is that IPS is placed in line and actively prevents or blocks detected intrusions, while IDS detects but does not respond to malicious activity.

The primary functions of an IPS are to monitor network traffic and compare it against predefined security rules or signatures, taking immediate action to prevent or thwart any suspicious or harmful activities. IPS technologies watch packet flows, enabling them to enforce secure protocols and deny the use of insecure protocols. They detect or prevent network security attacks like brute force attacks, Distributed Denial of Service (DDoS) attacks, and vulnerability exploits.

Key features and advantages that define IPS include:

  • Reinforced Security: IPS operates in parallel with other cybersecurity solutions and can identify threats that those solutions can’t, providing superior application security.
  • Customization: IPS can be set up with customized security policies to provide security controls specific to the enterprise.
  • Efficiency: By filtering out malicious activity before it reaches other security devices or controls, IPS reduces security teams’ manual efforts and enables other security products to perform more efficiently.

Intrusion Prevention Systems can be deployed as network-based intrusion prevention systems (NIPS), which monitor the entire network for suspicious traffic by analyzing protocol activity. They can also be integrated into unified threat management (UTM) solutions or next-generation firewalls.

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How Do Intrusion Prevention Systems Work?

Intrusion Prevention Systems work by analyzing network traffic in real-time and comparing it against known attack patterns and signatures. Here’s a step-by-step breakdown of how IPS functions:

  1. Traffic Monitoring: IPS continuously monitors network traffic, analyzing data packets as they traverse the network. It can inspect traffic at different OSI model layers, including the application, transport, and network layers.
  2. Signature-Based Detection: One of the primary methods IPS uses is signature-based detection. It maintains a database of known attack patterns, also known as signatures. These signatures represent the characteristics of known malware, viruses, and attack techniques. When IPS identifies a data packet that matches a signature, it takes action to block or quarantine the malicious traffic.
  3. Anomaly-Based Detection: In addition to signature-based detection, some IPS systems use anomaly-based detection. They establish a “normal” network behavior baseline by monitoring traffic patterns over time. When the IPS detects deviations from this baseline that could indicate an intrusion or abnormal activity, it raises alerts and can take preventive actions.
  4. Protocol Analysis: IPS examines network protocols and ensures they adhere to established standards. Any deviations from these standards may indicate a potential attack, and the IPS can respond accordingly.
  5. Deep Packet Inspection (DPI): DPI is a technique used by IPS to inspect the content of data packets deeply. It can analyze the payload of packets to detect specific attack patterns or malware signatures within the data.
  6. Active Responses: When suspicious or malicious activity is detected, the IPS can take various active responses, such as blocking traffic from the source, dropping malicious packets, or resetting connections. These actions combat cyber-attacks immediately.
  7. Logging and Reporting: IPS systems typically log detected incidents and generate reports. This information is invaluable for network administrators and security teams to analyze the threat landscape, understand attack patterns, and make informed decisions about network security.
  8. Continuous Updates: IPS systems require regular updates to their signature databases to remain effective. These updates ensure they can detect and respond to newly emerging threats and attack techniques.
  9. Integration with other Security Measures: IPS is often integrated with other security measures, such as firewalls and intrusion detection systems, to provide comprehensive network security. Together, these systems prevent and detect a wide range of threats.

Types of Attacks Prevented by Intrusion Prevention Systems

Intrusion Prevention Systems are designed to detect and prevent various types of network security attacks. Some of the common attacks that IPS helps prevent include:

  • Brute Force Attacks: These attacks involve an attacker attempting to gain unauthorized access to a system by trying multiple combinations of usernames and passwords.
  • Distributed Denial of Service (DDoS) Attacks: DDoS attacks involve multiple sources flooding a target system with traffic, making it difficult to mitigate the attack.
  • Vulnerability Exploits: IPS can detect and prevent attacks that leverage known vulnerabilities in software systems to gain control of a system.
  • Worms: Worms are self-replicating malware that can spread across a network, causing damage and disruption. IPS can help detect and block the spread of worms.
  • Viruses: IPS can also help detect and prevent the spread of viruses, which are malicious programs that can infect and damage systems.
  • Insecure Protocols: IPS can enforce secure protocols and deny using insecure protocols, such as earlier versions of SSL or protocols using weak ciphers.
  • Malicious Content Removal: After an attack, IPS can help remove or replace any remaining malicious content on the network, such as repackaging payloads, removing header information, and removing infected attachments from file or email servers.
  • Zero-day Exploits: Zero-day exploits target vulnerabilities that are not yet known or for which a patch has not been released. While IPS may not be able to detect and prevent all zero-day exploits, it can provide an additional layer of protection by blocking traffic that exhibits suspicious behavior or matches known attack patterns.

Benefits of Intrusion Prevention Systems

Intrusion Prevention Systems offer several benefits to organizations. Some of the most impactful advantages include:

Reduced Business Risks and Additional Security

IPS solutions help filter out malicious activity before it reaches other security devices or controls, reducing the manual effort of security teams and allowing other security products to perform more efficiently. They effectively detect and prevent vulnerability exploits and quickly block attacks that take advantage of newly discovered vulnerabilities.

Better Visibility Into Attacks and Improved Protection

Intrusion Prevention Systems use various detection methodologies to identify and stop attacks that firewalls, antivirus technologies, and other security controls may not automatically recognize. They can be customized to detect attacks and activities specifically of interest to the organization, such as policy violations or phishing attacks.

Increased Efficiency for Other Security Controls

By filtering out malicious traffic before it reaches other security devices and controls, IPS solutions improve the overall efficiency of the security infrastructure. They can also protect the availability and integrity of other enterprise security controls by analyzing incoming network traffic and blocking suspicious activity from reaching those controls.

Automated Threat Mitigation and Incident Reduction

IPS solutions help reduce network security incidents through automated threat mitigation, filtering out most security threats and freeing up IT staff from manual monitoring and management of network traffic. They can also ensure normal operations during DoS or DDoS attacks by stopping malicious traffic and maintaining availability.

Types of Intrusion Prevention Systems

Not all IPS solutions operate the same. In fact, there are four main types of IPS:

  • Network-based Intrusion Prevention System (NIPS): This type of IPS monitors the entire network for suspicious traffic by analyzing protocol activity. It is installed at strategic points to monitor all network traffic and scan for threats.
  • Wireless Intrusion Prevention System (WIPS): WIPS monitors Wi-Fi networks, acting as a gatekeeper and removing unauthorized devices.
  • Host-based Intrusion Prevention System (HIPS): HIPS is installed on individual hosts or endpoints and monitors their activities for malicious behavior.
  • Application-based Intrusion Prevention System (AIPS): AIPS focuses on monitoring and protecting specific applications or services, such as web servers or databases.

These types of IPS can be deployed individually or in combination to provide comprehensive network security. They are often integrated with other security tools, such as next-generation firewalls (NGFWs) or unified threat management (UTM) solutions, to enhance network visibility and automate threat response.

IPS vs IDS: Similarities and Differences

Intrusion Prevention Systems (IPS) and Intrusion Detection Systems (IDS) are essential components of network security strategies but have key differences in functionality and purpose. Here are the main similarities and differences between IPS and IDS:


  • IPS and IDS protect network infrastructure by detecting threats through network traffic analysis, either by comparing it against a database of known attack signatures or by monitoring for deviations from normal network behavior.
  • Both systems log monitored activity and actions taken, allowing for performance review and analysis.
  • IPS and IDS can learn to spot suspicious behaviors and minimize false positives.



  • IPS is a control-based solution that can accept or reject network packets based on predetermined rulesets, while IDS is a monitoring system that does not alter network traffic.
  • IDS operates across the enterprise network, monitoring and analyzing traffic in real-time, while IPS is typically deployed inline, directly in the network path, to actively block or remediate threats.
  • IDS only provides alerts about potential incidents, leaving the security team to decide on the appropriate action, while IPS takes action to block or remediate the detected threat.
  • IPS can potentially impact network performance due to the delay caused by inline processing, while IDS does not affect network performance as it is deployed in a non-inline manner.
  • IDS is often used initially to observe system behavior without blocking anything, and once fine-tuned, IPS can be deployed inline to provide full protection.

How Proofpoint Can Help

Proofpoint’s Emerging Threats Intelligence (ET Intelligence) is a comprehensive solution that provides timely and accurate information about suspicious and malicious activities. It offers fully verified intelligence, including deeper context, history, and detection information, helping organizations research threats and investigate incidents.

ET Intelligence delivers actionable threat intelligence feeds, which can be directly integrated with various security systems, including SIEMs, firewalls, intrusion detection systems (IDS), intrusion protection systems (IPS), and authentication systems.

With its advanced rule set and fully verified intelligence, Proofpoint’s ET Intelligence solutions can enhance the capabilities of IPS by providing additional context and integration with other security tools. By integrating Proofpoint’s ET Intelligence with IPS, organizations can strengthen their security posture and better protect their networks and systems from evolving cyber threats.

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