Zeek

Zeek manages gaining deep visibility into network activity, a task that is increasingly complex in modern network environments. Unlike active defense mechanisms like firewalls or intrusion prevention systems, Zeek operates passively, analyzing network traffic in real-time without interfering with the flow of data.

Technically, Zeek is deployed on sensors that can be hardware, software, virtual, or cloud-based, and it captures high-fidelity transaction logs, file contents, and other customizable data outputs. The tool uses an event engine to analyze live or recorded network traffic, generating neutral event logs that include detailed information about network protocols, application layer decoding, anomaly detection, and connection analysis. Zeek's scripting language allows for the creation of site-specific monitoring policies and the integration of additional analyzers, such as those built using the Spicy framework.

Operationally, Zeek requires careful placement of network taps or the use of switch SPAN ports to gain access to the desired network traffic. The logs generated by Zeek can be written to local disk or remote storage and are often integrated into SIEM systems for further analysis. A key consideration is the high volume of logs generated, with over 70 log files provided by default, which can impact storage and query performance. Additionally, while Zeek is highly adaptable and flexible, its performance can be affected by the complexity of the network and the volume of traffic being analyzed.

From a technical details perspective, Zeek tracks over 3,000 network events and supports a wide range of protocols through its built-in analyzers. The logs are highly detailed, as seen in the example of the conn.log which includes fields such as timestamp, source and destination IP and port, protocol, and connection state. This level of detail is crucial for threat hunting and comprehensive network security monitoring.