Zeek is a network security monitoring and traffic analysis framework rather than a traditional signature-based IDS. It transforms network traffic into rich, structured metadata that can be searched, correlated, and analyzed to identify suspicious activity and support incident investigations.
Zeek generates protocol-specific logs that describe network activity in a structured format. Common examples include conn.log for connection metadata, dns.log for DNS activity, http.log for web traffic, and TLS-related logs for encrypted communications. These records allow analysts to investigate behavior without manually reviewing packet captures.
💡 Pro Tip: Zeek's dns.log is extremely useful for identifying suspicious patterns such as DNS beaconing, algorithmically generated domains, and unusual query frequencies. Investigate recurring queries in context before concluding they are malicious.
This example extracts DNS queries from a JSON-formatted Zeek log and counts their frequency. High-volume or highly repetitive domains may warrant additional investigation.
Zeek is a cornerstone technology for Network Security Monitoring (NSM). By collecting metadata about connections, protocols, files, and certificates, analysts can reconstruct attack timelines, identify lateral movement, and investigate potential data exfiltration. In many cases, metadata provides valuable investigative context even when payload content is unavailable.
⚠️ Zeek deployments can generate significant log volumes in busy environments. Implement log retention policies, rotation, compression, and centralized storage to prevent disk exhaustion and maintain long-term visibility.
| Log File | Content | Common Use Case |
|---|---|---|
| conn.log | Connection metadata | Lateral movement and scan detection |
| dns.log | DNS activity | Beaconing and domain investigations |
| files.log | Observed file transfers | Malware download investigations |
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