Network Sniffers
Core Technology
Learn what's going on in your network, using Linux and its arsenal of packet capture tools.
We are always told that eavesdropping is bad. In social relations, that's probably true, but in computing (especially networking) where this activity is known as sniffing, it's an indispensable debugging technique. What goes in the wire is an ultimate answer to "What you've thrown at my service?" and "How did I reply?" Debugging aside, network sniffers may collect statistics or perform security monitoring. Linux comes with many tools of this kind, both GUI and terminal based. In this Core Tech, we'll discover perhaps the most popular one (or just my favorite).
Although sniffing is a legitimate technique, it is still largely prohibited in corporate environments. Many ISPs deem it illegal, too, so be careful when experimenting. A virtual machine based dedicated test lab is the safest option. Anyway, employ common sense and don't sniff traffic that could be sensitive, even if your housemates or colleagues are careless enough to send it unencrypted.
Back to the Beginning
Any network sniffer relies on the operating system's ability to forward it to all packets the network card receives, regardless of which process (or even host) they really target. The exact way of doing this is platform-specific. In Linux, packet sockets are the standard mechanism [1].
[...]
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
US / Canada
UK / Australia