The Internet's original design provided a modicum of privacy for users; it was not always possible to determine where a device was or who was using it. But a combination of changes, including “free” Internet services, increasing use of mobile devices to access the network, and the coming “Internet of Things” (sensors everywhere) make surveillance much easier to achieve and privacy more difficult to protect. Yet there are also technologies that enable communications privacy, including address anonymizers and encryption. Use of such technologies complicate law-enforcement and national-security communications surveillance, but do not completely block it. Privacy versus surveillance in Internet communications can be viewed as a complex set of economic tradeoffs–for example, obtaining free services in exchange for a loss of privacy; and protecting communications in exchange for a more expensive, and thus less frequently used, set of government investigative techniques–and choices abound.