How to Use the Command 'zeek' (with examples)
Zeek is a powerful passive network traffic analyzer that allows users to monitor network communications in real time or through saved packet capture (PCAP) files. It helps in understanding network traffic by providing detailed logs and information on network activities, which can be crucial for security analysis, troubleshooting, and network performance monitoring. Zeek processes network traffic and outputs useful data in various log files, typically stored in the current working directory. Learn how to perform network analysis with Zeek using different options and inputs.
Use case 1: Analyze live traffic from a network interface
Code:
sudo zeek --iface interface
Motivation:
This is a fundamental use case for network administrators and security analysts. By analyzing live traffic, they can proactively monitor what is happening within their network environment. Continuous monitoring assists in detecting unusual activities, identifying bandwidth usage patterns, and potentially spotting security threats as they occur in real time.
Explanation:
sudo: Because network interface analysis requires access to low-level system resources, the command must be executed with elevated privileges.zeek: Invokes the Zeek network analyzer.--iface interface: Specifies the network interface (e.g., eth0, wlan0) from which to analyze live traffic. Here, “interface” should be substituted with the actual name of the network interface you wish to monitor.
Example output:
Upon execution, Zeek will generate various log files such as conn.log, http.log, etc., in the current directory, providing insights on different types of network activities.
Use case 2: Analyze live traffic from a network interface and load custom scripts
Code:
sudo zeek --iface interface script1 script2
Motivation:
This use case is significant for users who wish to apply customized monitoring or security rules tailored to their network’s specific needs. Custom scripts allow for advanced detection and logging of particular traffic patterns, security threats, or network anomalies beyond Zeek’s default configuration.
Explanation:
sudo: Needed for privilege elevation as before.zeek: This engages Zeek to perform the analysis.--iface interface: Identifies the source of live traffic as described earlier.script1 script2: Refers to custom Zeek scripts that the user has developed to perform particular analysis tasks or detection mechanisms beyond the out-of-the-box capabilities.
Example output:
The output will include not only standard log files but also logs or alerts generated by custom scripts that address specific requirements such as detecting potential data exfiltration attempts.
Use case 3: Analyze live traffic from a network interface, without loading any scripts
Code:
sudo zeek --bare-mode --iface interface
Motivation:
Utilizing bare mode is beneficial when the administrator desires minimalistic analysis, reducing overhead to focus strictly on raw traffic data. This can be useful in scenarios where system resources are limited or when the focus is solely on performance monitoring without additional processing.
Explanation:
sudo: Required for permission to access the network interface.zeek: Calls the Zeek analyzer.--bare-mode: This flag tells Zeek not to load its default or any custom scripts, thus performing a very basic analysis of the traffic.--iface interface: Points to the network interface for live traffic monitoring.
Example output:
Operation in bare mode results in limited logging with basic capture of network sessions, excluding detailed parsing or analysis provided by scripts.
Use case 4: Analyze live traffic from a network interface, applying a tcpdump filter
Code:
sudo zeek --filter path/to/filter --iface interface
Motivation:
Applying a tcpdump filter allows administrators to focus on specific types of traffic. This is crucial in high-traffic environments where users may require filtering out noise to concentrate on particular applications, protocols, or suspicious activities.
Explanation:
sudo: Important for gaining necessary access to perform the analysis.zeek: Engages the Zeek tool.--filter path/to/filter: Specifies the path to atcpdumpfilter file which defines the criteria for filtering traffic, such as IP addresses, ports, or protocols of interest.--iface interface: Points to the live traffic interface.
Example output:
Logs produced will be contingent upon the filter criteria, showing only relevant traffic entries that satisfy the defined filter.
Use case 5: Analyze live traffic from a network interface using a watchdog timer
Code:
sudo zeek --watchdog --iface interface
Motivation:
The watchdog timer is vital for maintaining the stability and responsiveness of the Zeek process. It is particularly useful in long-term or continuous monitoring scenarios, where it helps prevent system hang-ups by monitoring and managing Zeek’s resource usage.
Explanation:
sudo: Necessary to carry out operations that require elevated privileges.zeek: Starts the Zeek process.--watchdog: Activates a watchdog timer which ensures that the Zeek process remains operational by monitoring its execution time and aborting it if it is perceived to be hung.--iface interface: Identifies the source of live traffic for monitoring.
Example output:
The watchdog feature typically results in standard log outputs, but may include logs of watched activities if the process is aborted due to an overrun.
Use case 6: Analyze traffic from a PCAP file
Code:
zeek --readfile path/to/file.trace
Motivation:
Analyzing offline traffic from a PCAP file offers investigators the chance to dissect past network activity. This is immensely advantageous for forensic analysis and post-breach investigations, where retaining and scrutinizing historical data can be critical for understanding the scope and details of an incident.
Explanation:
zeek: The main utility for running the analysis.--readfile path/to/file.trace: This argument specifies the path to a pre-captured PCAP file which carries recorded network traffic. Zeek will analyze this file as if it’s observing live traffic, respecting the data it contains.
Example output:
The result of this operation is a set of logs similar to analyzing live traffic. These logs provide insights into communications that occurred over the captured period.
Conclusion:
Using Zeek to analyze network traffic provides crucial insights into network behavior, security posture, and performance issues. Each of the use cases explored allows users to customize how they gather and interpret network data, catering to both real-time and historical data analysis needs. Whether used for routine network monitoring or comprehensive investigation post-incident, Zeek is a valuable tool in the cybersecurity and network analysis toolkit, offering significant flexibility and comprehensive data capture capabilities.
