How Do Network Sniffer Software Tools Work?

By Jack SteinLast Updated September 9, 2020
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Network sniffers, as their name suggests, work by "sniffing" at the bundles of data — which are what make up the internet traffic that comes from everyday online browsing and other activities online — that flow along a network of computers. The process, however, involves more than "sniffing"; network sniffers intercept, capture and analyze the data that are traveling to their destination in packets.

The sniffer then interprets the captured packets of data and consolidates them into information that humans can comprehend. The process is akin to eavesdropping on a conversation, but instead of sounds and words, sniffers are listening in on the streams of data. Also known as packet, wireless and Ethernet sniffers; packet analyzers; network probes; and snoops, sniffers are usually software tools but may also come in the form of hardware devices. Learn more about how they work to better understand how the internet works as a whole.

Network Sniffers Are the Eavesdroppers of Computer Conversations

Computers within a network communicate by sending packets of data out into the network and to other computers and servers, which are like transfer stations that direct data bundles where they need to go. Only the intended destination computer receives the data, while the other computers should ignore it altogether. The raw data traveling through the local network is unintelligible because it's broken down into packets and is often encrypted, which means it's scrambled so unintended recipients like hackers can't understand or access it.

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Once the packet reaches its destination, the computer reassembles the data packets and then responds accordingly. These back-and-forth exchanges between computers in a local network take place constantly, and the speed of communication is measured in megabytes and gigabytes per second.

To illustrate further, imagine a room with 10 people. The people represent computers and the room is the computer network. When one person says something to another in the room, only the person to whom they're speaking will hear and respond to the message, while the others will tune out of the conversation. Someone with a network sniffer, on the other hand, will be hanging on every word of that conversation.

Instead of ignoring the communications between computers in a local network, a computer with a network sniffer listens in by keeping its network interface card (NIC) open. It takes a snapshot of the data packets passing through, reassembles them and then displays the decoded information on the user interface.

There Are Several Legitimate Uses for Network Sniffers

Network sniffers are not entirely new programs. Network administrators and information technology (IT) experts have long used them to analyze and improve network speed and performance. Analyzing data that comes from these monitoring tools helps network administrators detect bottlenecks that are slowing down the flow of data and can also provide information about how to resolve these issues.

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Analyzing patterns in the flow of data packets enables network administrators to identify potential problems that can cause outages and network downtime. This gives them enough time to take measures to prevent interruptions in network processing and the flow of online traffic. Because network monitoring sniffer tools also provide administrators with an overview of network traffic volumes, they can more accurately predict when a system upgrade becomes necessary to handle heavier traffic.

Network sniffers can also play a critical role in early detection of network security vulnerabilities and even intrusion attempts. Programmers can configure them to work with alongside security applications to help prevent network breaches. Among the most popular network monitoring tools for business use are LogicMonitor, Paessler and Spiceworks.

Network Sniffers Have More Nefarious Real-World Applications, Too

Understanding how network sniffers work will can make it easier to understand how people can abuse these tools. Apart from the regular data exchanges between computers in a local network, sniffers can also collect information such as port numbers, internet protocol (IP) addresses and application details. Hackers can use this information to hack into networks and computers to steal users' personal data. The availability of free network sniffers has also made it possible even for amateur hackers to snoop around unsecured Wi-Fi networks.

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The most obvious concern about network sniffers is that they're capable of gathering a computer user’s credentials, including login and password details, via an unsecured network. Whenever a user signs into a personal account online, the user sends data out into the computer network, and network sniffers can intercept this information. This is one of the main reasons why users of free public Wi-Fi, such as that available in cafes, airports and hotel lounges, are told to use the service with caution or not at all.

Of course, some establishments offering public Wi-Fi are conscientious enough to use security measures such as password protection and data encryption to protect their patrons. There are also simple but effective ways of protecting yourself from malicious network sniffers. Your best bet is avoiding the use of public Wi-Fi (unsecured, password-free) altogether.

If you need to use public Wi-Fi, avoid websites that require you to log in and type in a password. Do not conduct any financial transactions online unless you use a secure network like your internet connection at home. It's also a good idea to use a virtual private network (VPN), which encrypts the relay of data between your computer and a website so others can't "read" it even if they access it.