Sniffing

A sniffer is a type of eavesdropping program that monitors information traveling over a network. When used legitimately, sniffers can help identify potential network trouble-spots, but when used for criminal purposes, they can be damaging and very difficult to detect. Sniffers enable hackers to steal proprietary information from anywhere on a network, including passwords, e-mail messages, company files, and confidential reports.

Sniffing attacks have caused major data breaches. For instance, in 2013, five hackers were charged in a worldwide scheme that targeted the corporate networks of retail chains such as 7-Eleven and the French retailer Carrefour SA, using sniffer programs to steal more than 160 million credit card numbers. This case illustrates how sniffers can be used to harvest sensitive data flowing through corporate networks at very large scale.

E-mail wiretaps are a variation on the sniffing threat. An e-mail wiretap is a method for recording or journaling e-mail traffic generally at the mail server level from any individual. E-mail wiretaps are used by employers to track employee messages and by government agencies to surveil individuals or groups. The USA PATRIOT Act permits the FBI to compel ISPs to install a black box on their mail servers that can impound the e-mail of a single person or group for later analysis.

A man-in-the-middle (MitM) attack also involves eavesdropping but is more active than a sniffing attack, which typically involves passive monitoring. In a MitM attack, the attacker is able to intercept communications between two parties who believe they are directly communicating with one another, when in fact the attacker is controlling the communications. This allows the attacker to change the contents of the communication — for example, altering an order amount or payment instruction in transit.