Programs that tap into a computer network with the purpose of intercepting data traveling between two network machines are called sniffing software. This type of software program can be used to intercept and interpret data on a computer or network, including browser passwords, chat programs, user settings and network traffic. Sniffing software can also be known as a packet scanner, a packet analyzer or a network analyzer. Types of this software include Internet protocol (IP) sniffing software, hypertext markup language (HTML) sniffing software, port scanners, and packet sniffing programs. Software used for network sniffing is most often used legitimately by network administrators to identify the source of communication problems among different network machines.
When network traffic should be flowing but is not flowing properly, sniffing can help the person responsible for maintaining the network gather more information that can help solve the problem. Network problems can occur on the entire network, with specific servers, or when data transfers only among specific network machines. Using software made for network data analysis, the administrator can determine the nature of the problem, the machines affected by the problem and determine computer and network settings which could be contributing to network slowness.
Sniffing can be done through a wireless connection, or it can be performed using software installed on a computer that is part of the wired network. Common programs used for sniffing include Carnivore ™, snoop™ and SkyGrabber™. Not all sniffing is done using sniffing software. Network administrators often have hardware scanners that perform network analysis. Hardware that analyzes network data includes Bluetooth™-based sniffing devices and analysis hardware that taps straight into a computer port.
Though sniffing software is usually used by networking professionals to analyze and troubleshoot network traffic, it can also be used for criminal purposes. Viruses embedded in downloaded software can include sniffing viruses that record and interpret data entered into the computer. Many data sniffing viruses are designed to glean passwords and financial information from computers that have been infected with data sniffing viruses.
Most people use the term "sniffer" to refer to any packet analyzing software, but the word Sniffer™ is trademarked by Network Associates, the maker of the Sniffer Network Analyzer. The term sniffer came into common use because a common non-trademarked slang term for the act of using packet analyzing software to listen in on network traffic is "sniffing," and when a user operates sniffing software to listen in on network traffic, he is said to be using the software to sniff the connection.