Network sniffers monitor network data. A sniffer can be a self-contained software program or a hardware device with the appropriate software or firmware programming. Sniffers usually act as network probes or "snoops." They examine network traffic, making a copy of the data without redirecting or altering it. Some sniffers work only with TCP/IP packets, but the more sophisticated tools can work with many other protocols and at lower levels including Ethernet frames.
Years ago, sniffers were tools used exclusively by network engineers. Today, however, these utilities have become popular on the Internet with hackers and the merely curious. The U.S. Federal Bureau of Investigation (FBI) has utilized a famous sniffer system called "Carnivore" to help detect illegal Internet communications.
Also Known As: network monitor