Zeek

Zeek is a powerful open-source network security monitor that turns raw traffic into rich, structured logs of connections, protocols, files, and application-layer activity for threat hunting and NSM.

Network Security open-source network-security-monitoring threat-hunting incident-response

Overview

Zeek (formerly Bro) is a free and open-source network security monitoring (NSM) framework developed by the International Computer Science Institute (ICSI) and now maintained by the Zeek Project. Unlike signature-based IDS tools, Zeek parses network traffic at the application layer and produces rich, structured logs in TSV or JSON format covering connections, DNS, HTTP, SSL/TLS, SMTP, FTP, SMB, files, and more. Analysts use Zeek logs for threat hunting, incident response, network baselining, and retrospective analysis. Zeek supports a Turing-complete scripting language for custom protocol parsers and detection logic, cluster deployment for high-throughput networks, and integration with SIEM platforms and tools like RITA, AC Hunter, and Elastic Security.

Primary Use Cases

✔ Generating rich, structured network logs (conn, dns, http, ssl, files, smtp, smb) for threat hunting, incident response, and network baselining.

✔ Extracting files transferred over the network (HTTP, SMB, SMTP, FTP) for malware analysis and evidence preservation during incident response.

✔ Custom detection engineering with the Zeek scripting language to write protocol parsers, threat signatures, and network behavior analytics.

Frequently Asked Questions

Yes. Zeek is released under the BSD 3-Clause license and is maintained by the Zeek Project, a non-profit organization. It is free for both personal and commercial use with no licensing fees.

As of September 2026, the current stable release is Zeek 7.x, building on the major 6.x LTS line. Recent releases have focused on performance improvements, expanded protocol analyzers, better cluster management, and tighter integration with JSON-based pipelines and SIEM platforms.

Suricata and Snort are signature-based IDS/IPS engines that alert on known malicious patterns. Zeek is a network security monitor that focuses on rich, structured logging and protocol-level visibility rather than signature matching. Zeek is often deployed alongside Suricata so that Suricata provides signature alerts while Zeek provides the detailed context needed for investigation and threat hunting.

Yes. Zeek supports cluster deployment, where traffic is load-balanced across multiple worker nodes coordinated by a manager and proxy. Combined with AF_PACKET or PF_RING for efficient packet capture, Zeek clusters can handle high-throughput environments including 10G, 40G, and beyond when properly sized.

Zeek is available as a package on most Linux distributions (apt, yum/dnf), as a Docker image, and as source builds from the official Zeek repository. Once installed, you configure the interfaces to monitor, choose which protocol analyzers to enable, and set the log output directory. Many organizations deploy Zeek alongside Suricata and feed logs into Elastic Security, Splunk, or a dedicated NSM stack like Security Onion.

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Category Info

Network Security covers tools and platforms used to monitor, inspect, and defend network traffic against intrusions, malicious activity, and data exfiltration across enterprise and cloud environments.

Added On

September 16, 2026

Last Updated

September 16, 2026