Exploring Network Traffic Analysis with Pyshark and Wireshark Dissectors

February 11, 2024

Network traffic analysis plays a crucial role in understanding and troubleshooting network communications. It allows us to inspect packets and gain insights into the behavior and performance of network applications. In this article, we will explore how to perform network traffic analysis using Pyshark, a powerful Python package that serves as a wrapper for Wireshark’s tshark command-line utility.

Reading from a Capture File

Pyshark provides a simple and convenient way to read packets from a capture file. With just a few lines of code, you can start extracting valuable information from your network captures. Here’s an example:

import pyshark

# Open the capture file
cap = pyshark.FileCapture('/tmp/mycapture.cap')

# Access the first packet
print(cap[0])

In this example, we open a capture file using the FileCapture class and access the first packet using indexing. Pyshark automatically parses the packets using the installed Wireshark dissectors, allowing us to easily access packet details such as source and destination addresses, protocols, and more.

Reading from a Live Interface

Pyshark also enables real-time packet capturing from live interfaces. This is especially useful for monitoring network traffic and troubleshooting issues in real-time. Here’s an example:

import pyshark

# Create a live capture on the specified interface
capture = pyshark.LiveCapture(interface='eth0')

# Sniff packets for a specific timeout (in seconds)
capture.sniff(timeout=50)

# Access the captured packets
print(capture[3])

# Continuously sniff packets for a specific number of counts
for packet in capture.sniff_continuously(packet_count=5):
print('Just arrived:', packet)

In this example, we create a LiveCapture instance on the specified interface (eth0). We can then use the sniff method to capture packets for a specific timeout. We can access and process the captured packets using the same techniques as reading from a capture file. The sniff_continuously method allows us to continuously capture packets for a specified number of counts.

Decrypting Packet Captures

Sometimes, we need to decrypt captured traffic to analyze its contents. Pyshark supports automatic decryption of traces using the WEP, WPA-PWD, and WPA-PSK standards. Here’s an example:

import pyshark

# Decrypt a capture file using a password
cap = pyshark.FileCapture('/tmp/capture1.cap', decryption_key='password')

# Decrypt live captured packets with an encryption type
capture = pyshark.LiveCapture(interface='wi0', decryption_key='password', encryption_type='wpa-psk')

In this example, we use the decryption_key parameter to specify the password used for decryption. We can also specify the encryption type using the encryption_type parameter. Pyshark provides the SUPPORTED_ENCRYPTION_STANDARDS attribute to check the supported encryption standards for each capture class.

Using Display Filters

Pyshark display filters allow us to focus on specific protocols or packets of interest. While BPF filters offer filtering capabilities, Wireshark’s display filters provide more flexibility for analyzing application-focused traffic. Here’s an example:

import pyshark

# Read from a capture file with a display filter
cap = pyshark.FileCapture('/tmp/capture1.cap', display_filter="dns")

# Read from a live interface with a display filter
capture = pyshark.LiveCapture(interface='en0', display_filter="tcp.analysis.retransmission")

In this example, we pass the display_filter parameter to specify the display filter we want to apply on the capture. This allows us to focus only on packets related to DNS or TCP retransmissions, making our analysis more targeted and efficient.

Pyshark provides a rich set of features and options for network traffic analysis. Whether you’re reading from capture files, live interfaces, or remote interfaces, Pyshark simplifies the process and allows for easy extraction of packet data. It’s an excellent tool for analyzing network traffic and gaining valuable insights into network communications.

Conclusion

In this article, we explored network traffic analysis using Pyshark, a Python package that acts as a wrapper for Wireshark’s tshark utility. We learned how to read packets from capture files, live interfaces, and remote interfaces using Pyshark’s intuitive API. We also discovered features such as decrypting captured traffic and using display filters to focus on specific protocols or packets of interest. With Pyshark, performing network traffic analysis becomes more accessible and convenient.

Category: Networking

Tags: Python, Network Traffic Analysis, Wireshark, Pyshark, Capturing Network Packets, Wireshark Dissectors, Parsing Network Packets, Decrypting Captured Traffic, Display Filters, Live Interfaces, Remote Interfaces

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