Ethical Hacking: Techniques, Tools, and Countermeasures, 4th Edition

Sniffers

A sniffer is a software application or device that is designed to capture, or “sniff,” network traffic as it travels across a network. Sniffers provide the ability to observe or steal information that may not otherwise be available. A sniffer can give an attacker access to a large amount of information, including email passwords, application software passwords, File Transfer Protocol (FTP) credentials, and email contents, as well as any files transferred over a network.

NOTE

Like most technologies, sniffers are not inherently good or evil—it all depends on the intent of the user of the technology. In the hands of a network administrator, a sniffer can be used to diagnose network problems and uncover design problems in the network. ...