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Packet Sniffing

Definition: Packet sniffing is a network monitoring technique used to intercept and log traffic that passes over a digital network or part of a network. As data travels over the network, it is broken up into smaller pieces or packets, which a packet sniffer can capture and analyse.

In cyber security, packet sniffing can serve both legitimate and malicious purposes. Network administrators use packet sniffers for monitoring and diagnosing network health and performance issues, ensuring network traffic optimisation, and auditing network security compliance. Conversely, cyber attackers may use packet sniffing to eavesdrop on network traffic, steal sensitive data, and gather intelligence for further attacks such as MITM (Man-in-the-Middle) attacks.

The effectiveness of packet sniffing as a malicious tool is highly dependent on the network environment. Encrypted communications, such as those using TLS/SSL, can provide protection against sniffing by making intercepted data unreadable. However, if attackers have the necessary encryption keys or can bypass the encryption through other means, they can still gain access to the content of the communications.

Key Characteristics:

  • Traffic Capture: Collects packets that flow through a network segment.
  • Passive Monitoring: Usually operates without sending data on the network, making it hard to detect.
  • Analysis and Inspection: Offers detailed information about network packets, including source and destination addresses, content, and protocols used.
  • Use by Network Management Tools: Employed by legitimate software to administer networks efficiently.


  • Real-World Example: During a routine security audit, a company’s network administrator uses packet sniffing to verify that no confidential data is being sent out unencrypted.
  • Hypothetical Scenario: A cybercriminal connects to a public Wi-Fi network and runs a packet sniffer to capture login credentials sent over unencrypted connections.

Related Terms:

  • Wiretap: A method similar to packet sniffing where communications are intercepted, typically over a telephone line or within software communications.
  • Encryption: The process of encoding information in such a way that only authorised parties can access it, often used to protect data from being read by packet sniffers.
  • Network Traffic Analysis: The process of capturing, forwarding, and analysing network traffic to determine performance, security, and/or general network operations.

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