Brief Rundown of Technology:
Wiretapping, also known as lawful interception, is the practice of intercepting telecommunications covertly. Traditionally, wiretapping was used to monitor telephone conversations, but with the huge increase in Internet usage, wiretapping has come to include monitoring internet telecommunications. The old version of wiretapping revolved around the electric current flowing throughout a phone line. Agents who wished to listen in on someone's conversation would have to physically plug a device into the subject's phone line and interpret the electric fluctuations that represented the sounds of the conversation. If you think about it, the second phone in your household is a wiretap; by tapping into the line, you can hear everything that's said over that phone line. The diagram below demonstrates how wiretapping was done in the old days.
However, today's telecommunication is done on the digital level. As most people know, the digital age transmits data and information by encoding them into discrete pulses most people know as bits of 0's and 1's before transmission over the physical medium. Both telephone and internet telecommunications are transmitted via these packets of bits. Digitizing data allows more telecommunications to share the same physical medium, often known as the backbone. Phone and internet companies have a huge network of these backbones which carry the majority of the data. Thus, today, government agents can just plug into the backbone to tap into any line that backbone services.
Wiretapping has come to encompass more than just the monitoring of voice data. Internet packets can also be tracked through what are called "packet sniffers." A packet sniffer is similar to a wiretap in that it eavesdrops on telecommunication and records what it thinks is relevant, just that it does it for Internet communication, not voice communication. Packet sniffers can filter on a variety of criteria, such as the source, destination, type of communication, or communiqué content.
How packet sniffing works.
Wiretapping has a rich history of usage in criminal investigations and matters of national security. Past wiretapping has generally revolved around telephone conversations, as the government was slow to adapt to the Internet age. When the government swung its focus to Internet communications, the FBI developed the Carnivore packet sniffer.
In 1997, the FBI employed an outside contractor to develop Carnivore, a customizable packet sniffer which could filter packets to pick up only what the specific surveillance target was communicating. While the FBI didn't really release many details, it is generally agreed upon that an individual Carnivore system was composed of a Microsoft Windows workstation with packet sniffing software and a removal disk drive. Each Carnivore system had to be installed at the Internet Service Provider of the surveillance target so that it could home in on the target's Internet communications. Not only did Carnivore record the packets in question, it would reconstruct emails and Web pages so that the FBI could see exactly what the target was seeing.
Carnivore was met with some controversy, as common people believed that all their Internet traffic was being monitored. According to the official reports, Carnivore was only used after securing warrants and only recorded packets related to the surveillance target. Traffic unrelated to the surveillance target would just be ignored.
In 2005, the FBI announced that they had discontinued use of the Carnivore system and its derivatives. Instead, they opted to use more up-to-date systems developed by the private sector. Official reports indicated that Carnivore was only used 13 times during its entire lifespan.