Even in the earliest days of telephones and telegraphs, people were concerned about wiretapping. In the 1860s, before the modern telephone was even invented, many state courts in the United States enacted statutes that prohibited anybody from listening in on telegraph communication. By the 1890s, the modern telephone was in widespread use -- and so was wiretapping. From that time on, it has been illegal in the United States for an unauthorized person to listen in on somebody else's private phone conversation. In fact, it is even illegal to record your own phone conversation if the person on the other end is not aware that you're recording it.
Historically, the law has not been as strict for the government. In 1928, the United States Supreme Court approved the practice of wiretapping for the police and other government officials, though some states have banned it. In the 1960s and 1970s, this authority was curtailed somewhat. Law enforcement now needs a court order to listen in on private conversations, and this information can be used in court only in certain circumstances.
Additionally, the court order will only allow the authorities to listen in on a call for a certain length of time. Even under this tight control, the practice of government wiretapping is highly controversial. Civil-liberties advocates point out that when you tap a phone line, you are not only invading the subject's privacy, but also the privacy of the person the subject is talking to.
With the expansion of the Internet, many new concerns have come up. Modems use phone lines the same way traditional telephones do, but instead of transmitting a pattern of electricity that represents sounds, they transmit a pattern that represents the bits and bytes that make up Web pages and e-mail. The government (and others) can view this information using packet sniffers, such as the FBI's Carnivore system. Since it's not actually verbal conversation, Internet communication is not protected by the same laws that protect traditional phone use. But in 1986, the U.S. government enacted the Electronic Communications Privacy Act (ECPA), wiretapping regulation that protects e-mail, pagers and cell phone calls.
Many organizations, including the American Civil Liberties Union (ACLU), hold that the ECPA does not do enough to protect individual privacy. They charge that the act is not nearly as stringent as older wiretapping laws. Their primary arguments are that the authorities are allowed to monitor these communication lines in a much wider range of circumstances, and that there are too many judicial officials who can approve the wiretap. Also, only the content of the communication is afforded protection. The government is free to monitor who's communicating with whom, and how often.
Data encryption technologies are helping to curtail unauthorized wiretapping to some degree, but as encryption capabilities expand, so do wiretapping techniques. In the future, wiretapping probably won't be as easy as connecting a phone to the line outside somebody's house, but it will almost certainly continue in some form or another. Whenever information is transmitted from point to point, there is the possibility that a spy will intercept it along the way. This is nearly unavoidable in a global communications system.
To learn more about traditional wiretapping, modern wiretapping and the controversy surrounding government wiretapping, check out the links below.