Active vs. Passive Network Sniffing: Key Differences Explained

This article explores the differences between active and passive network sniffing, common techniques used in cybersecurity. Network sniffing, a form of eavesdropping, involves capturing network packets, often with the intent of intercepting unencrypted credentials.

What is Network Sniffing?

Network sniffing is a type of attack where an attacker intercepts data packets traversing a wired or wireless network. It’s essentially electronic eavesdropping. The primary goal is often to capture unencrypted usernames, passwords, and other sensitive information.

Common protocols vulnerable to sniffing attacks include:

• FTP
• HTTP
• SMTP
• NNTP
• POP
• IMAP
• Telnet

The most effective defense against sniffing is to use encrypted protocols, making it significantly harder to decipher captured traffic.

Network sniffing can be broadly classified into two main categories: active and passive sniffing.

Active Sniffing

• In active sniffing, the attacker directly interacts with the target machine. They send packets to the target and analyze the responses.
• Active sniffing typically occurs in switched networks. The attacker attempts to “poison” the switch by flooding it with bogus MAC addresses.
• Examples of Active Sniffing:
  • ARP Spoofing
  • MAC Flooding
  • HTTPS and SSH Spoofing
  • DNS Spoofing

Passive Sniffing

• In passive sniffing, the attacker doesn’t interact directly with the target. They simply “listen” to network traffic, capturing packets transmitted and received by the network or exchanged between two machines.
• Passive sniffing commonly occurs in hub-based networks. The attacker connects to the hub from their machine. An attacker typically needs an account on the LAN.
• Examples of Passive Sniffing:
  • Hub-based Networks
  • Wireless Networks