Zeek — Network Security Monitor
Why It Matters
Signature-based IDS tools scream when they see something they know. Zeek works differently. It doesn’t just throw alerts; it records what’s going on in the network in detail. Logs for connections, DNS lookups, HTTP sessions, TLS handshakes. That context matters: instead of one-off alerts, analysts see the bigger picture. That’s why many SOCs keep Zeek running as a core data source.
How It Works
Zeek runs off a mirror port or TAP, watching traffic in real time. It parses dozens of protocols — HTTP, DNS, SMTP, FTP, TLS, and more — then turns them into structured logs. Those logs show who talked to whom, what domains were queried, what files moved across. On top of that, Zeek has its own scripting language. Teams write policies to detect odd behavior or extract extra data. Most setups feed Zeek logs into SIEM or ELK stacks where analysts can dig deeper.
Technical Notes
| Area | Notes |
| OS support | Linux, BSD, macOS |
| Purpose | Network security monitoring (NSM) |
| Output | Detailed logs: connections, DNS, HTTP, TLS, files |
| Extensible | Custom scripts in Zeek language |
| Integrates | SIEM, ELK stack, Splunk, hunting pipelines |
| License | BSD, open source |
Deployment Notes
– Install from packages or source.
– Hook up an interface to mirrored traffic.
– Start with default policies.
– Ship logs to a SIEM or just store them locally.
– Add custom scripts once you know what gaps you need to fill.
Where It Fits
– SOC teams that want rich network evidence.
– Threat hunters checking for behavior, not just signatures.
– Researchers digging into protocol traffic.
– Enterprises with high traffic where basic IDS is too shallow.
Caveats
– Generates logs, not verdicts — analysts must interpret.
– Data volume is heavy; plan disk and retention early.
– Learning curve steeper than Snort/Suricata.
– Without integration into SIEM/log pipeline, value is limited.