[Cyber Security Terms](/glossary) Intrusion Detection System [Blog](/blog)[Breaches](/breaches)[Resources](/resources)[News](/news) [Cyber Security Terms](/glossary) # Intrusion Detection System ##### [Catherine Chipeta](/team/catherine-chipeta) updated Oct 17, 2021 ###### Contents ## What is an Intrusion Detection System? An [intrusion detection system (IDS)](https://www.upguard.com/blog/intrusion-detection-system) identifies cyber attacks on a network or a host. Such attacks could include [botnets](https://www.upguard.com/blog/what-is-a-botnet), [Distributed Denial of Service (DDoS)](https://www.upguard.com/blog/what-is-a-ddos-attack), and [ransomware](https://www.upguard.com/blog/ransomware). The system analyzes and monitors suspicious network activity, [vulnerability exploits](https://www.upguard.com/blog/vulnerability), or policy violations via sensors placed on network devices or the host. IDSs report any identified threats to an administrator or a [security information and event management (SIEM) system](https://www.upguard.com/blog/what-is-third-party-risk). ## Types of Intrusion Detection Systems ### By Detection Method * Signature-based Detection * Anomaly-based Detection * Reputation-based Detection * Stateful Protocol Analysis Detection ### By Network Placement * [Network Intrusion Detection System (NIDS)](https://www.upguard.com/blog/top-free-network-based-intrusion-detection-systems-ids-for-the-enterprise) * [Host Intrusion Detection System (HIDS)](https://www.upguard.com/blog/tripwire-enterprise-vs-ossec-fee-or-free-which-is-better) ## Key takeaways * Intrusion detection systems help information security teams identify cyber threats faster and more effectively. * They operate by analyzing and monitoring traffic using specially-placed sensors. * IDSs can use a range of different detection methods and operate on a network or host level. * * ###### Reviewed by No items found. ###### Author ##### [Catherine Chipeta](/team/catherine-chipeta) ###### Reviewed by ##### [Kaushik Sen](/team/kaushik-sen) ###### Join 27,000+ cybersecurity newsletter subscribers ## Read more about Intrusion Detection Systems Learn more about Intrusion Detection System and the latest issues in cybersecurity. [UpGuard](/blog/intrusion-detection-system) [Intrusion Detection Systems (IDS): Types, How They Work, and Tools](/blog/intrusion-detection-system) #### [Intrusion Detection Systems (IDS): Types, How They Work, and Tools](/blog/intrusion-detection-system) An intrusion detection system (IDS) is a software application or hardware device that detects cyber attacks. Learn more about how it works and its uses. [](/team/catherine-chipeta) [Catherine Chipeta](#) July 28, 2026 [UpGuard](/blog/siem) [What is SIEM?](/blog/siem) #### [What is SIEM?](/blog/siem) SIEM delivers next-generation cybersecurity functionality for businesses in real-time, covering the key challenges of modern cybersecurity. Learn more. 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