There's no better way to see what's on your network.

Corelight Sensors extract over 400 data elements from network traffic in real time, with open-source Bro - using a format that was chosen by incident responders, for incident responders. When your team can work faster, the network is safer.

Download Bro Logs: a selection

Use Cases

How people use Zeek.

Zeek’s (formerly known as Bro) exceptional data and flexible scripting language have inspired security and operations teams around the world to find creative applications for the open-source platform. Here are just a few examples:

Threat hunting

Assessing the scope of a malware attack

Pivot off a malware hash in Zeek’s files.log to immediately see all other hosts in an environment that have downloaded the malicious file and then prioritize additional incident response work such as agent deployment.


Locating PCAP files needed for an investigation

Pivot from the logs of a Zeek-parsed connection directly into connection packets in Moloch using the shared Community ID appended to the Zeek conn.log.

Verifying containment and remediation

Use Zeek’s network logs for conducting post-breach monitoring to look for the recurrence of malware beaconing.

Improving defensibility

Use Zeek’s continuous logging across protocols to establish the "ground truth" of what happened historically, minimizing both legal expenses and the scope of disclosure.

Threat detection

Detecting hidden C2 server communications

Uncover live C2 communications via Zeek’s dpd.log when an attacker attempts to disguise their C2 traffic in a purported SSL connection.

close dpd-bro-log

Lateral movement detection

Detect lateral movement in MITRE ATT&CK related to SMB and DCE-RPC traffic, such as indicators targeting Windows Admin Shares and Remote File Copy or stream Zeek logs to the Real Intelligence Threat Analytics (RITA) tool to create a daily report of potential beaconing activity.

Detecting off-port protocol usage

Use Zeek’s deep protocol parsing capabilities to identify network services, such as HTTP or DNS, running on non-standard ports.

Fingerprinting connections for fraud detection

Create custom Zeek logs to fingerprint connections and identify issues like API fraud and account takeovers.

Investigating unauthorized SMB file access

Use Zeek’s SMB logs as a source of evidence to document end user access to a sensitive SMB file share without authorization.

Data enrichment

Enhance traffic monitoring with local context

Use the Zeek Input Framework to append internal server names and IT contact information fields to the conn.log to accelerate investigations and remediation workflows.

Enhancing DNS visibility

Use Zeek’s dns.log—which contains both queries and responses—to access forensic information server logs can’t provide, due to a lack of detail.


Identifying vulnerable software

Use Zeek’s software.log to identify outdated or vulnerable software, such as Java or Flash, running in an environment.


Flagging Cyrillic keyboard usage

Monitor Zeek’s rdp.log to identify the use of Russian character set keyboards in an environment, which could signal unusual behavior.


Verifying that sensitive connections use strong encryption

Verify via Zeek’s ssl.log that all TLS sessions for sensitive connections use appropriately strong ciphers, and prompt security ops staff to take remedial action if less secure ciphers are detected.


Network operations

Creating inventories of connected devices

Inventory network-connected devices and their services without needing to install host agents, and use Zeek’s software.log to monitor BYO software used by employees.

Monitoring risky SSL certificates

Monitor self-signed and expired, or soon-to-expire, certificates via Zeek’s ssl.log.

Troubleshooting a load balancer issue

Diagnose a load balancer performance problem that is difficult or impossible to replicate in a lab environment via evidence gathered from Zeek’s network logs and end finger pointing between security and network operations teams.