Packet sniffing refers to the use of an appliance or program (known as a “packet analyzer”) to capture data packets or data units that cross a network. A network packet contains information about the user, its source and destination, and its user’s browser version, among others. Packet sniffing decodes the content of these packets for later inspection, but it cannot change it.

Through this mechanism, security engineers can analyze and monitor network traffic and determine if the packets are formatted as per Internet standards. By doing so, they can ensure that the packet contents are not forged or malicious.

Packet sniffing also ensures that a network is functioning correctly. It allows engineers to troubleshoot network latency or speed. It also assists in identifying the network’s traffic pattern or how traffic travels from one node to another.

Interestingly, nefarious actors also employ packet sniffing to steal user data. However, they can only accomplish this if security vulnerabilities exist in your network or if you use weak credentials for your accounts.

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For a better understanding of what packet sniffing is, let’s take a look at the Open Systems Interconnection (OSI) model, which manages the Internet.

The OSI model is a network stack composed of seven layers that facilitate how the Internet works. Each layer represents a protocol (e.g., File Transfer Protocol [FTP], Internet Protocol Version 4 [IPv4], or Secure Socket Shell [SSH]) or hardware (e.g., a coaxial cable) that links one to the other. These layers allow you, the end-user, to access information on the Internet or communicate with other users. In the simplest terms, the OSI relays information until it reaches end-users.

The problem with this relay function is that it’s not inherently secure. Protocols or standard sets of rules associated with each layer are not encrypted and do not have protection embedded in them. However, users can rely on standardized security overlays to remedy this problem. Such solutions now comprise networking and cybersecurity best practices today.

Packet sniffing occurs when a threat actor successfully positions a packet analyzer in a network that runs one or a combination of the OSI layer’s protocols. The sniffer can intercept the contents of packets sent between users through devices, firewalls, and local area networks (LANs). Cybersecurity analysts also use the same technology to fend off attacks coming from these threat actors.

Illegal Motivations for Packet Sniffing

Unfortunately, threat actors also use packet sniffing to snoop on targets. In fact, they have written several packet sniffing tools. Spyware, for example, are categorized as packet sniffers. Hackers use these to look into a user’s browsing history, chats, and other online conversations. Worse, they use the tools to manipulate network traffic to gather sensitive information about a user, including logins and bank information.