Network protocol analyzers, also known as packet sniffers or packet analyzers, are software tools used to monitor, capture, analyze, and interpret network traffic. They play a critical role in understanding the behavior and performance of computer networks, helping administrators, analysts, and security professionals gain insights into the communication patterns and issues within a network.
These analyzers intercept and examine the data packets that traverse a network. Data packets are the fundamental units of information exchanged over a network, containing information about the source and destination addresses, the protocol being used, and the actual data being transmitted.
Network protocol analyzers offer the following capabilities:
- Packet Capture: They capture data packets as they move through the network, providing a comprehensive view of device communication.
- Packet Analysis: They dissect the captured packets to extract information such as source and destination IP addresses, port numbers, protocol types, and payload data.
- Protocol Decoding: They interpret the network protocols used in the packets, such as Ethernet, IP, TCP, UDP, HTTP, etc. This helps in understanding the structure and purpose of the data being exchanged.
- Traffic Monitoring: By examining the data flow patterns, these tools allow network administrators to monitor network performance, identify bottlenecks, and troubleshoot issues.
- Security Analysis: Network protocol analyzers are also used for security purposes. They can help detect suspicious or malicious activities, such as unauthorized access attempts, data breaches, and malware infections.
- Troubleshooting: When network issues arise, these tools assist in identifying the root causes by analyzing packet-level details, revealing anomalies or misconfigurations.
- Performance Optimization: By examining network traffic patterns and data exchanges, analyzers can aid in optimizing network resources for better performance.
- Traffic Filtering: Users can set up filters to capture only specific types of traffic, particularly useful for focusing on relevant data or specific problems.
This article delves into a selection of prominent network protocol analyzers, shedding light on tools like Kismet, KisMAC, tcpdump, and Wireshark.
Kismet
Kismet is a potent wireless protocol analyzer available on various platforms such as Linux, Mac OS X, and even the embedded OpenWRT Linux distribution. It functions with wireless cards supporting passive monitor mode. Kismet passively logs all 802.11 frames to disk or the network in standard PCAP format, suitable for later analysis using tools like Wireshark. Additionally, Kismet provides associated client information, AP hardware fingerprinting, Netstumbler detection, and GPS integration. As a passive network monitor, it can even identify “closed” wireless networks by analyzing traffic sent by wireless clients. Multiple instances of Kismet can run simultaneously, reporting to a central user interface over the network. This facilitates wireless monitoring over extensive areas like universities or corporate campuses. Kismet operates within the radio card’s passive monitor mode, ensuring no data transmission. It’s an invaluable tool for diagnosing wireless network issues.
KisMAC
Exclusive to the Mac OS X platform, KisMAC offers functionalities similar to Kismet. Still, with a sleek graphical interface tailored for Mac OS X. As a passive scanner, KisMAC logs data to disk in PCAP format, compatible with Wireshark. It supports passive scanning with AirportExtreme cards and various USB wireless adapters.
tcpdump
Tcpdump is a command-line utility for monitoring network traffic. While lacking the extensive features of Wireshark, it uses fewer resources. Tcpdump can capture and display network protocol data to the link layer, presenting packet headers and data received. It offers filtering for specific criteria, allowing only displaying relevant packets. Captured packets can be loaded into Wireshark for visual analysis and further diagnostics. Tcpdump is a standard tool in Unix derivatives (Linux, BSD, and Mac OS X).
Wireshark
Formerly known as Ethereal, Wireshark is a free network protocol analyzer for both Unix and Windows platforms. Wireshark facilitates the examination of live network data or data from a stored capture file, enabling interactive browsing and sorting of captured data. Each packet offers summary and detailed information, including full headers and data portions. Wireshark boasts powerful features like a comprehensive display filter language and the ability to view the reconstructed stream of a TCP session. It may be overwhelming for first-time users or those unfamiliar with the OSI layers. Typically employed to isolate and analyze specific traffic to/from an IP address, Wireshark can also serve as a versatile troubleshooting tool. For example, it can identify machines infected with network worms or viruses by detecting machines sending similar types of TCP/IP packets to numerous IP addresses.
