One important, and disturbing, aspect of packet sniffers is their ability to place their host machine's network adapter into 'promiscuous mode.' When network adapters are in promiscuous mode, they not receive only the data directed to the machine hosting the sniffing software, but also all other data traffic on the physically connected local network. Are sniffers really so readily available? A quick search for network sniffers will confirm that there are numerous Web sites rife with software sniffers able to run on just about any operating system. This brings the art of network sniffing to anyone who wants to perform this task. More recently, advances in technology have allowed for the development of software sniffers. Years ago, sniffers were hardware devices that were physically connected to the network. Unfortunately, they are sometimes hard to detect. When used by malevolent individuals, however, sniffers can also represent a significant threat to your network. When used by systems administrators, network sniffers can be invaluable tools for diagnosing or troubleshooting network problems.

The term packet sniffing refers to the technique of copying individual packets as they traverse a network. Sniffers are tools - sometimes referred to as network analyzers - commonly used for monitoring network traffic.

Packet sniffing tools