The Best Packet Sniffers Reviewed in 2023 (Free + Paid)

A packet sniffer or network analyzer is a tool that intercepts and captures data packets as they travel over a network. When devices communicate with each other over a network, the information is divided into smaller units called packets.

A packet sniffer “sniffs” or listens to the network traffic and captures these packets.

This guide highlights the best packet sniffing tools on the market helping you to choose from the dozens of options out there.

Here’s our list of the best packet sniffers:

1. SolarWinds Deep Packet Inspection and Analysis Tool EDITOR’S CHOICE Gives detailed insights into what causes network slowness and uses deep packet inspection to allow you to resolve the root causes. You can identify traffic by application, category and risk level to eliminate and filter problem traffic. With a great user interface, this excellent packet sniffing tool is perfect for network analysis. Download a 30-day free trial.
2. ManageEngine NetFlow Analyzer (FREE TRIAL) A traffic analysis tool that works with NetFlow, J-Flow, sFlow Netstream, IPFIX, and AppFlow. Start a 30-day free trial.
3. Paessler Packet Capture Tool A packet sniffer, a NetFlow sensor, an sFlow sensor, and a J-Flow sensor built into Paessler PRTG.
4. Omnipeek Network Protocol Analyzer A network monitor that can be extended to capture packets.
5. tcpdump The essential free packet capture tool that every network manager needs in his toolkit.
6. Windump A free clone of tcpdump written for Windows systems.
7. Wireshark A well-known free packet capture and data analysis tool.
8. tshark A lightweight answer to those who want the functionality of Wireshark, but the slim profile of tcpdump.
9. NetworkMiner A Windows-based network analyzer with a no-frills free version.
10. Fiddler A packet capture tool that focuses on HTTP(s) traffic.
11. Capsa Written for Windows, the free packet capture tool can be upgraded for payment to add on analytical features.

The best packet sniffers

The tools I’ve listed in this article can be used by experienced network admins who already know what they’re looking for, but aren’t sure which tools are best. They can also be used by more junior sysadmins to gain experience with how modern networks look during day-to-day operations, which will help identify network issues later on.

Almost all of these tools collect in the same way; it’s the analysis that differentiates them.

1. SolarWinds Deep Packet Inspection and Analysis tool (FREE TRIAL)

SolarWinds is a comprehensive suite of IT management tools. The tool that is more relevant to this article is the Deep Packet Inspection and Analysis tool.

Key Features:

• Categorizes network traffic
• Protocol stack analyzer
• Live monitoring
• Supports traffic shaping
• 30-day free trial

Why do we recommend it?

The Deep Packet Inspection and Analysis Tool is part of the SolarWinds Network Performance Monitor. This on-premises software package checks on the statuses of network devices with the Simple Network Management Protocol as its main task. So, the DPI system is supplementary to that central function and adds on greater detail of network activity without users having to buy an additional network traffic analyzer. Most of your traffic will have encrypted contents and this DPI system can’t break that confidentiality. However, it reads the unencrypted headers of packets traveling around the network, which provide data on protocols and endpoints involved in network traffic creation.

Collecting network traffic activity is relatively straightforward. Using tools like WireShark, basic level analysis isn’t a show stopper either. But not all situations are that cut and dried. In a bustling network, it may be hard to determine even some fundamental things such as:

• What application on the local network is creating this traffic?
• If the application is known (say, a web browser) where are people spending most of their time?
• Which connections take the longest and are bogging down the network?

Most network devices just use each packet’s metadata to ensure the packet gets where it is going. The contents of the packet are unknown to the network device. Deep Packet Inspection is different; it means that the actual contents of the packet are inspected to learn more about it.

Critical network information that cannot be gleaned from the metadata can be discovered in this way. Tools like those provided by SolarWinds can provide more meaningful data than simply traffic flow.

Other techniques for managing high volume networks include NetFlow and sFlow. Each has its strengths and weaknesses and you can read more about NetFlow and sFlow techniques here.

Network analysis, in general, is an advanced topic that is half experience and half training. It’s possible to train someone to understand every detail about network packets. Still, unless that person also has knowledge of the target network, and some experience to identify anomalies, they won’t get very far.

Who is it recommended for?

The SolarWinds Network Performance Monitor is a great tool for automated monitoring of mid to large networks. It can also be used to centralize the monitoring of multiple networks. There isn’t a free version of this package, so cash-strapped small businesses probably won’t go for it. However, the addition of DPI on top of autodiscovery, network inventory management, and automated monitoring with alerts makes this package very good value for money. You need to have a host running Windows Server to install this package.

You can enhance your ability to examine packets by adding on the NetFlow Traffic Analyzer. This module includes a packet sniffer and also flow protocols, such as NetFlow and IPFIX. You can get the pair of tools together in the Network Bandwidth Analyzer Pack.

SolarWinds Network Bandwidth Analyzer Pack Get a 30-day FREE Trial

2. ManageEngine NetFlow Analyzer (FREE TRIAL)

The ManageEngine NetFlow Analyzer takes traffic information from your network devices. You can choose to sample traffic, capture entire streams, or gather statistics on traffic patterns with this tool.

Key Features:

• SNMP-based
• Traffic shaping
• NetFlow, IPFIX, sFlow, J-Flow, NetStream, AppFlow

Why do we recommend it?

ManageEngine NetFlow Analyzer is a traffic monitoring tool that mainly uses network device query languages, such as NetFlow, sFlow, and J-Flow. These systems analyze packets and store statistics related to packet header values within the switch or router. So, when the ManageEngine monitor queries that information, it is retrieving data that was derived from packet inspection. Packet capture can take up a lot of space on a hard drive because a typical network processes a very large volume of traffic. So, just extracting statistics about packet headers gives you a more efficient method of conducting protocol analysis.

The makers of network devices don’t all use the same protocol for communicating traffic data. Thus, the NetFlow Analyzer is capable of using different languages to gather information. These include Cisco NetFlow, Juniper Networks J-Flow, and Huawei Netstream. It is also capable of communicating with the sFlow, IPFIX, and AppFlow standards.

The monitor is able to track the consistency of data flows as well as the load on each network device. Traffic analysis capabilities let you see packets as they pass through a device and capture them to file. This visibility will enable you to see which network applications are chewing up most of your bandwidth and take decisions over traffic shaping measures, such as priority queuing or throttling.

The dashboard of the system features color-coded graphics, which make your task of spotting problems a lot easier. The attractive look and feel of the console ties in with other ManageEngine infrastructure monitoring tools because they were all built on a common platform. This makes it integrate with several ManageEngine products. For example, it is very common for network administrators to buy both the OpManager and the NetFlow Analyzer from Manage Engine.

OpManager monitors devices’ statuses with SNMP procedures, which NetFlow Analyzer focuses on traffic levels and packet flow patterns.

ManageEngine NetFlow Analyzer installs on Windows, Windows Server, and RHEL, CentOS, Fedora, Debian, SUSE, and Ubuntu Linux. The system is offered in two editions.

The Essential edition gives you the standard network traffic monitoring functions plus a reporting and billing module. The higher plan is called the Enterprise Edition. This has all of the features of the Essential Edition plus NBAR & CBQoS monitoring, an advanced security analytics module, capacity planning utilities, and deep packet inspection capabilities. This Edition also includes IP SLA and WLC monitoring.

Who is it recommended for?

Any network administrator that needs to analyze traffic and try to get the best value for money out of current hardware would benefit from this package. The tool is also able to assist in implementing traffic shaping measures that ensure your time-critical traffic gets delivered speedily without having to buy extra capacity. This system is available in a free edition but that will only give you data extraction from two interfaces, which isn’t much use. There is a version of the software that will analyze a single network and another that can monitor a WAN. You need to install and manage the software for the NetFlow Analyzer and it will run on Windows Server or Linux. You can also get it on an AWS account.

You can get either edition of the NetFlow Analyzer on a 30-day free trial.

ManageEngine NetFlow Analyzer Start a 30-day FREE Trial

3. Paessler Packet Capture Tool (FREE TRIAL)

The Paessler Packet-Capture-Tool PRTG: All-In-One-Monitoring is a unified infrastructure monitoring tool. It helps you manage your network and your servers. The network monitoring segment of the utility covers two types of tasks. These are a network performance monitor, which examines the statuses of network devices and a network bandwidth analyzer, which covers the flow of traffic over links in the network.

Key Features:

• Four packet capture sensors
• Live traffic graphs
• Performance troubleshooting
• Traffic alerts

Why do we recommend it?

The Paessler Packet Capture Tool is part of the PRTG bundle. This is a collection of “sensors” – each of which is an individual monitoring system. The tool offers value for money because you can just add it on to the full network performance monitor, which is driven by the Simple Network Management Protocol. The PRTG bundle also offers NetFlow, sFlow, and J-Flow sensors. You probably won’t need to activate all of those options. Combining one or two of these sensors with the packet capture sensor for ad-hoc investigations and referring to the live network map that PRTG provides gives you great support for traffic management.

The bandwidth analysis part of PRTG is implemented through the use of four different packet capture tools. These are:

• A packet sniffer
• A NetFlow sensor
• An sFlow sensor
• A J-Flow sensor

The PRTG packet sniffer only captures the headers of the packets traveling across your network. This gives the packet analyzer a speed advantage and it also reduces the amount of storage space needed to hold capture files. The dashboard of the packet sniffer categorizes traffic by application type. These include email traffic, web packets, chat app traffic data, and file transfer packet volumes.

NetFlow is a very widely used data flow messaging system. It was created by Cisco Systems but it is also used for equipment produced by other manufacturers. The PRTG NetFlow sensor also picks up IPFIX messages — this messaging standard is an IETF-sponsored successor to NetFlow. The J-Flow method is a similar messaging system used by Juniper Networks for its equipment. The sFlow standard samples traffic flows, so it will collect every nth packet. NetFlow and J-Flow both capture continuous streams of packets.

Paessler prices its PRTG software on the number of “sensors” that an implementation activates. A sensor is a system condition or hardware component. For example, each of the four packet sniffers offered by Paessler counts as one PRTG sensor. The system is free to use if you activate 100 sensors or less, so if you only use this package for its packet sniffing interfaces, you won’t have to pay Paessler anything.

Who is it recommended for?

PRTG is a very big package but you can choose to tailor it by only activating a limited number of sensors. This makes the system very accessible for businesses of all sizes and it also comes with the capability to monitor multiple networks from one console. Small businesses are able to use this system at no cost because it is free forever if you only activate 100 sensors. The software package installs on Windows Server but PRTG is now also available as a SaaS package on the cloud.

The Paessler system includes many other network and server monitoring capabilities including a virtualization monitor and an application monitor. PRTG can be installed on-premises or you can access it as a cloud service. The software runs on Windows environments and you can get it on a 30-day free trial.

Paessler Packet Capture Tool PRTG Download 30-day FREE Trial

4. Omnipeek Network Protocol Analyzer

LiveAction Omnipeek, previously a product of Savvius, is a network protocol analyzer that can be used to capture packets as well as produce protocol analysis of network traffic.

Key Features:

• Protocol analyzer
• Packet capture tool
• Also for wireless networks

Why do we recommend it?

Ominpeek Protocol Analyzer will sample passing packets on a specific network device, compiling statistics on traffic source, destination, and protocol. The service can also be set to capture packets for viewing. However, you would only be interested in looking at packet headers for analysis and the Ominpeek does that for you in its default settings. The Omnipeek Protocol Analyzer will also sample traffic on wireless networks. This system can be set up to provide traffic analysis for all network traffic or just that traffic intended for one specific device interface – so you can examine a specific link.

Omnipeek can be extended by plug-ins. The core Omnipeek system doesn’t capture network packets. However, the addition of the Capture Engine plug-in gets the packet capture function.  The Capture Engine system picks up packets on a wired network; another extension, called Wifi Adapter adds wireless capabilities and enables Wifi packets to be captured through Omnipeek.

The functions of the base Omnipeek Network Protocol Analyzer extend to network performance monitoring. As well as listing traffic by protocol, the software will measure the transfer speed and regularity of traffic, raising alerts if traffic slows down or trips passed boundary conditions set by the network administrator.

The traffic analyzer can track end-to-end transfer performance across an entire network, or just monitor each link. Other functions monitor interfaces, including incoming traffic arriving at web servers from outside the network. The software is particularly interested in traffic throughput and a display of traffic per protocol. Data can be viewed as lists of protocols and their throughput or as live graphs and charts. Packets captured with the Capture Engine can be stored for analysis or replayed across the network for capacity testing.

Who is it recommended for?

Omnipeek can be used for traffic investigations if you want to see which system or user is generating the most load on the network. IT can also be used as a live network performance monitor because you can set up data throughput expectation thresholds that will trigger alerts if crossed. This is an on-premises package for Windows.

Omnipeek installs on Windows and Windows Server. The system isn’t free to use. However, it is possible to get Omnipeek on a 30-day free trial.

5. tcpdump

The fundamental tool of almost all network traffic collection is tcpdump. It is an open-source application that comes installed on almost all Unix-like operating systems. Tcpdump is an excellent collection tool and comes complete with a very complex filtering language. It’s essential to know how to filter the data at collection time to end up with a manageable chunk of data to analyze. Capturing all data from a network device on even a moderately busy network can create too much data to analyze efficiently.

Key Features:

• Command-line tool
• Packet capture
• Free to use

Why do we recommend it?

The tcpdump system has been in circulation for a very long time. This is the classic network packet capture tool that was originally written for Unix. You can just display packets on the screen, but it is more usual to write to file. Although you can impose some command line filters on the output, either for display on the screen to reduce the amount of traffic that goes to a file, this is a raw capture tool. You won’t want to leave this system running for too long because it will generate very large files.

In some rare cases, allowing tcpdump to output its capture directly to your screen may be enough to find what you’re looking for. For example, in writing this article, I captured some traffic and noticed that my machine was sending traffic to an IP address I did not recognize. It turns out that my machine was sending data to a Google IP address of 172.217.11.142. Since I did not have any Google products running, nor Gmail open, I did not know why this was happening. I examined my system and found this:

[ ~ ]$ ps -ef | grep google
user      1985  1881  0 10:16 ?        00:00:00 /opt/google/chrome/chrome --type=service

It seems that even when Chrome is not running in the foreground it remains running as a service. I would not have necessarily noticed this without a packet analysis to tip me off. I re-captured some more tcpdump data but this time told tcpdump to write the data to a file that I opened in Wireshark (more on that later). Here’s that entry:

Tcpdump is a favorite tool among sysadmins because it is a command-line tool. This means that it doesn’t require a full-blown desktop to run. It is unusual for production servers to provide a desktop because of the resources that would take, so command-line tools are preferred. As with many advanced tools, tcpdump has a very rich and arcane language that takes some time to master.

Who is it recommended for?

The tcpdump system is a little dated as an analysis tool – you can use GUI tools for easier analysis. However, it is a very useful “nuts and bolts” packet sniffer. You can use tcpdump for free but there isn’t a version for Windows. There are some clones available that third parties have created for use on Windows – see below for one example.

A few of the very basic commands involve selecting the network interface from which to collect data, and writing that data to a file so it can be exported for analysis elsewhere. The -i and -w switches are used for this.

# tcpdump -i eth0 -w tcpdump_packets
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
^C51 packets captured

This produces a capture file:

file tcpdump_packets
tcpdump_packets: tcpdump capture file (little-endian) - version 2.4 (Ethernet, capture length 262144)

The standard TCP capture file is a pcap file. It is not text so it can only be read by an analysis program that knows how to read pcap files.

6. WinDump

Most useful open source tools are eventually cloned to other operating systems. When this happens, the application is said to have been ported over. WinDump is a port of tcpdump and behaves in very similar ways.

Key Features:

• Tcpdump for Windows
• Works with WinPcap
• Free to use

Why do we recommend it?

WinDump is one of the adaptations available to get tcpdump on Windows. This is probably the most well known option for packet sniffing on Windows but it isn’t the only one available. The program relies on WinPcap, but so do many other packet detection systems, such as Wireshark. So, once you install WinPcap you will have a number of packet sniffing options for Windows.

One major difference between WinDump and tcpdump is that Windump needs the WinpCap library installed prior to being able to run WinDump. Despite both WinDump and WinpCap being provided by the same maintainer, they are separate downloads.

WinpCap is an actual library that needs to be installed. But, once it is installed, WinDump is an .exe file that needs no installation so it can just run. That may be something to keep in mind if you’re running a Windows network. You don’t necessarily need WinDump installed on every machine since you can just copy it over as needed, but you will want WinpCap installed to support WinDump.

As with tcpdump, WinDump can output network data to the screen for analysis, be filtered in the same way, and also write data to a pcap file for analysis offsite.

Who is it recommended for?

WinDump is for network administrators who only have Windows PCs to work on and don’t have the option of using tcpdump. As with tcpdump, WinDump is not such a good choice for packet analysis. You would be better off storing packets to a file and then searching through them with a better analysis tool. As it is free to use, WinDump is an appealing little utility to have installed just in case.

7. Wireshark

Wireshark is probably the next best-known tool in any sysadmin’s toolkit. It can not only capture data, but also provides some advanced analysis tools. Adding to its appeal, Wireshark is open source, and has been ported over to almost every server operating system that exists. Starting life named Ethereal, Wireshark now runs everywhere, including as a standalone portable app.

Key Features:

• Essential tool for networks
• Query language
• Free to use

Why do we recommend it?

Wireshark is a much better packet analyzer than the WinDunp/tcpdump option. This system can identify multiple networks and capture traffic from one at a time. You can filter packets during detection and then examine the collected packets with the same query language. The Wireshark tool is able to show you packets live and you can then choose to store those to a file. Packets can be read in from a file for analysis as well. The service automatically color-codes packets and it will also let you step through a conversation, which makes the full examination of the many packets that go into forging a connection much easier to detect.

If you’re analyzing traffic on a server with a desktop installed, Wireshark can do it all for you. The collected packets can then be analyzed all in one spot. However, desktops are not common on servers, so in many cases, you’ll want to capture the network data packets remotely and then pull the resulting pcap file into Wireshark.

At first launch, Wireshark allows you to either load an existing pcap file, or start capturing. If you elect to capture network traffic, you can optionally specify filters to pare down the amount of data Wireshark collects. Since its analysis tools are so good, it’s less important to ensure you surgically identify the data at collection time with Wireshark. If you don’t specify a filter, Wireshark will simply collect all network data that your selected interface observes.

One of the most useful tools Wireshark provides is the ability to follow a stream. It’s probably most useful to think of a stream as an entire conversation. In the screenshot below we can see a lot of data has been captured, but what I am most interested in is that Google IP address. I can right-click it and Follow the TCP Stream to see the entire conversation.

If you’ve captured traffic elsewhere, you can import the pcap file using Wireshark’s File -> Open dialogue. The same filters and tools that can be used for natively captured network data are available for imported files.

Who is it recommended for?

Students of network technology get taught how to use Wireshark. So, your first contact with this system will be during your training. Fortunately, the package is free to use. Once you have become familiar with the use of Wireshark, you will want to have in installed on your device for ad-hoc investigations. Everyone involved in network management probably already knows that they need Wireshark, and probably already has it.

8. TShark

TShark is a handy cross between tcpdump and Wireshark. Tcpdump excels at collecting data packets and can very surgically extract only the data you want, however it is limited in how helpful it can be for analysis. Wireshark does a great job at both collection and analysis, but since it has a heavy user interface, it can’t be used on headless servers. Enter TShark; it captures and analyzes but does the latter on the command line.

Key Features:

• Command line
• Based on Wireshark
• Free to use

Why do we recommend it?

TShark is the command line version of Wireshark. It is a useful option if you want to put scripts together to search through packet data live and discard the packets. This removes the need to store large amounts of data. You can select specific information, collate statistics, and write your own traffic monitoring system. The Wireshark system has its own quirky query language that takes a long time to learn. However, if you master it, switching over to TShark can make your queries automated and provide a method to create alerts and set up orchestration between applications.

TShark uses the same filtering conventions as Wireshark which should be no surprise since they’re essentially the same product. This command tells TShark only to bother capturing the destination IP address as well as some other interesting fields from the HTTP part of the packet.

# tshark -i eth0 -Y http.request -T fields -e ip.dst -e http.user_agent -e http.request.uri

172.20.0.122    Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0    /images/title.png
172.20.0.122    Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0    /images/styles/phoenix.css
172.20.0.122    Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0    /images/code/jquery_lightbox/jquery_lightbox/js/jquery-1.2.6.pack.js
172.20.0.122    Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0    /images/styles/index.css
172.20.0.122    Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0    /images/images/title.png
172.20.0.122    Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0    /favicon.ico
172.20.0.122    Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0    /favicon.ico

If you want to capture to a file you can use the -w switch to write it, and then use TShark’s -r (read mode) switch to read it.

Capture first:

# tshark -i eth0 -w tshark_packets
Capturing on 'eth0'
102 ^C

Read it, either on the same server, or transfer it to some other analysis server.

# tshark -r tshark_packets -Y http.request -T fields -e ip.dst -e http.user_agent -e http.request.uri
172.20.0.122    Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0    /contact
172.20.0.122    Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0    /reservations/
172.20.0.122    Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0    /reservations/styles/styles.css
172.20.0.122    Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0    /res/code/jquery_lightbox/jquery_lightbox/js/jquery-1.2.6.pack.js
172.20.0.122    Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0    /res/styles/index.css
172.20.0.122    Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0    /res/images/title.png

Who is it recommended for?

TShark is a good option for network specialists who have time to play around. If you are too busy with day-to-day tasks, you won’t really have time for TShark. The tool can be useful for quickly prototyping new applications that you want to develop. This tool is free to use and it is available for Windows, Unix, Linux, and macOS.

9. NetworkMiner

NetworkMiner is a fascinating tool that falls more into the category of a forensic tool rather than a straight-up network sniffer. The field of forensics typically deals with the investigation and collection of evidence and Network Miner does that job well for network traffic. Much like WireShark can follow a TCP stream to recover an entire TCP conversation, Network Miner can follow a stream to reconstruct files that were sent over the network.

To capture live traffic, Network Miner should be strategically placed on the network to be able to observe and collect the traffic you’re interested in. It won’t introduce any of its own traffic onto the network, so it operates very stealthily.

Key Features:

• Analysis tool
• Easy-to-use interface
• Free version

Why do we recommend it?

NetworkMiner should be considered as an alternative to Wireshark. The Wireshark system is great if you can remember all of the filtering commands. However, it can be time-consuming looking for the right keywords to use to make a proper analysis. NetworkMiner is easier to use because it has a simpler query language.

Network Miner can also operate in offline mode. You can use the tried and true tcpdump tool to capture packets at a point of interest on your network, and then import the pcap files into Network Miner. It will then attempt to reconstruct any files or certificates it finds in the capture file.

Network Miner is built for Windows, but by using Mono, it can be run on any OS that has a Mono framework such as Linux and macOS.

There’s a free version to get you started that has a decent array of features. If you want more advanced capabilities such as GeoIP location and custom scripting, you’ll need to purchase a professional license.

Who is it recommended for?

NetworkMiner is an option for people who just can’t deal with Wireshark. There is a free version of the system and a more powerful paid version. If you don’t like NetworkMiner either, you should focus on one of the NetFlow analyzer tools on this list. NetworkMiner runs on Windows and you can also get it on Linux or macOS through Mono.

10. Fiddler (HTTP)

Fiddler is not technically a network packet capture tool, but it is so incredibly useful that it made the list. Unlike the other tools listed here which are designed to capture ad-hoc traffic on the network from any source, Fiddler is more of a desktop debugging tool. It captures HTTP traffic and while many browsers already have this capability in their developer tools, Fiddler is not limited to browser traffic. Fiddler can capture any HTTP traffic on the desktop including that of non-web applications.

Many desktop network applications use HTTP to connect to web services and without a tool like Fiddler, the only way to capture that traffic for analysis is using tools like tcpdump or WireShark. However, those tools operate at the packet level so analysis includes reconstruction of those packets into HTTP streams. That can be a lot of work to perform some simple HTTP investigation and Fiddler comes to the rescue. Fiddler can help discover cookies, certificates, and packet payload data coming in or out of those apps.

Key Features:

• Displays HTTP traffic
• Debugging assistance
• Free to use

Why do we recommend it?

Fiddler examines HTTP traffic and it has a similar appearance to Wireshark because it color codes captured packets in the data viewer. This system is specifically designed for analyzing Web traffic and it can be very advantageous for those developing Web applications to work out exactly what their new code is doing behind the scenes.

It helps that Fiddler is free and, much like NetworkMiner, it can be run within Mono on any other operating system with a Mono framework.

Who is it recommended for?

Fiddler is intended for use by Web application developers and the IT operations teams that received newly developed code. This is a good tool for use in DevOps environments and it is available in both free and paid versions. This system will run on Windows but you can get it on Linux and macOS through Mono.

11. Capsa

Capsa Network Analyzer has several editions, each with varying capabilities. At the first level, Capsa free, the software essentially just captures packets and allows some very graphical analysis of them. The dashboard is very unique and can help novice sysadmins pinpoint network issues quickly even with little actual packet knowledge. The free level is aimed at people who want to know more about packets and build up their skills into full-fledged analysts.

The free version knows how to monitor over 300 protocols, it allows for email monitoring and also it can save email content and also supports triggers. The triggers can be used to set alerts for specific situations which means Capsa standard can also be used in a support capacity to some extent.

Key Features:

• Analyzes 300 protocols
• Interprets data into graphs
• Free version

Why do we recommend it?

Capsa Network Analyzer uses packet examination for protocol analysis and forms a live traffic monitor from these scans. You don’t need any specialist programming skills to use Capsa because it is driven by a GUI package. You can still filter traffic and adapt the display screens of the system.

Capsa is only available for Windows 2008/Vista/7/8 and 10.

Who is it recommended for?

This is a good tool for small businesses that need a free network monitoring tool. There are higher editions that are paid and more comprehensive. This is a protocol analyzer that shows live graphs of traffic per application. Capsa offers a similar experience to the ManageEngine NetFlow Analyzer but it is a lot simpler.

Choosing a packet sniffer

With the packet sniffing tools I have mentioned, it is not a big leap to see how a systems administrator could build an on-demand network monitoring infrastructure.

If the network is so large that this isn’t feasible, then enterprise-level tools like the SolarWinds suite and its 30-day free trial can help tame all that network data into a manageable data set.

Tcpdump, or Windump, could be installed on all servers. A scheduler, such as cron or Windows scheduler, could kick off a packet collection session at some time of interest and write those collections to a pcap file.

At some later time, a sysadmin can transfer those packets to a central machine and use Wireshark to analyze them.

Advantages of packet sniffing

A packet sniffer is a useful tool to enable you to implement your company’s network capacity policy. The main benefits are that they:

• Identify congested links
• Identify applications that generate the most traffic
• Collect data for predictive analysis
• Highlight peaks and troughs in network demand

The actions you take depend on your available budget. If you have the resources to expand network capacity, the packet sniffer will enable you to target new resources more effectively. If you have no budget, packet sniffing will help traffic shaping through prioritizing application traffic, resizing subnets, rescheduling heavy-traffic events, limiting bandwidth for specific applications, or replacing applications with more efficient alternatives.

Promiscuous mode

It is important to understand how the network card on your computer operates when you install packet sniffing software. The interface from your computer to the network is called the “network interface controller,” or NIC. Your NIC will only pick up internet traffic that is addressed to its MAC address.

To capture general traffic, you need to put your NIC into “promiscuous mode”. This removes the listening limit on the NIC. In promiscuous mode, your NIC will pick up all network traffic. Most packet sniffers have a utility within the user interface that manages the mode switch for you.

Network traffic types

Network traffic analysis requires an understanding of how networking works. There’s no tool that will magically remove the requirement for an analyst to understand the basics of networking such as the TCP three-way handshake which is used to initiate a connection between two devices. Analysts should also have some understanding of the types of network traffic that exist on a normally functioning network such as ARP and DHCP traffic. This knowledge is essential because analyzing tools will just show you what you ask for – it’s up to you to know what to ask for. If you’re not sure how your network looks normally, it can be hard to ensure you’re digging for the right thing in the mass of packets you’ve collected.

Enterprise tools

Let’s start at the top and work our way down into the nitty-gritty basics. If you’re dealing with an enterprise-level network, you’ll need the big guns. While almost everything uses tcpdump at its core (more on that later), enterprise-level tools can provide other analytical functions such as correlating traffic from many servers, providing intelligent query tools to spot issues, alerting on exception cases, and producing nice graphs that management demands.

Enterprise-level tools tend to focus on network traffic flow rather than judging packet content. By that, I mean that the focus of most sysadmins in an enterprise is to keep the network humming along without performance bottlenecks. When bottlenecks occur, the goal is usually to determine if the problem is the network or an application on the network. On the other side of the coin, these enterprise-level tools are usually able to see so much traffic that they can help predict when a network segment will saturate which is a critical element of capacity management.

Hacker tools

Packet sniffers are also used by hackers. Be aware that these tools can be used to attack your network as well as to solve problems. Packet sniffers can be used as wiretappers to help steal data in transit and they can also contribute to “man in the middle” attacks that alter data in transit and divert traffic in order to defraud a user on the network. Invest in intrusion detection systems to protect your network from these forms of unauthorized access

How do Packet Sniffers and Network Analyzers work?

The key feature of a packet sniffer is that it copies data as it travels across a network and makes it available for viewing. The sniffing device simply copies all of the data that it sees passing over a network. When implemented on a switch, settings of the device allow the passing packet to be sent to a second port as well as the intended destination, thus duplicating traffic. Usually, the packets of data that are reaped from the network get copied to a file. Some tools will also show that data in a dashboard. However, packet sniffers can gather a lot of data, which includes encoded admin information. You will need to find an analysis tool that can help you be dereferencing information on the journey of the packets in the extract and other pieces of information, such as the relevance of the port numbers that the packets travel between.

A straightforward packet sniffer will copy over all of the packets traveling on the network. This can be a problem. If t cases, the contents of the packet are not needed for network performance analysis. If you want to track network usage over a 24 hour period or over a few days, then storing every packet will occupy a very large amount of disk space — even if you are only taking in the packet headers. In these scenarios, it is advisable to sample packets, which means copy every 10th or 20th packet rather than copying over every single one.

Packet Sniffers FAQs