Where your online data get stored

Internet companies such as Apple, Facebook and Google have vast amounts of data on you.

These include the photos and video you share, the email you send and receive and the musings you broadcast to friends on what you are thinking or eating. Internet companies store all this information at data centers they run around the world. When you're ready to read your email, the message gets pulled from a computer at one of these centers. When you're sharing a photo, the image gets transmitted to one of these computers and stored there until someone else views it.

When the government requests information on a customer, with the presentation of a subpoena or court order, the Internet service company taps these same computers to access the data.

Now comes a report on a clandestine program code-named "PRISM." As described by The Washington Post, PRISM gives the U.S. government access to email, documents, audio, video, photographs and other data belonging to foreigners on foreign soil who are under investigation. The newspaper said participating companies and services include AOL Inc., Apple Inc., Facebook Inc., Google Inc., Microsoft Corp., Yahoo Inc., Skype, YouTube and Paltalk. Companies that responded to Associated Press inquiries say they only provide the government with user data required under the law.

In any case, like pieces of a puzzle, the bits and bytes left behind from people's electronic interactions can be cobbled together to draw conclusions about their habits, friendships and preferences using data-mining formulas and increasingly powerful computers.

It's all part of a phenomenon known as "Big Data," a catchphrase increasingly used to describe the science of analyzing the vast amount of information collected through mobile devices, Web browsers and check-out stands. Analysts use powerful computers to detect trends and create digital dossiers about people.

It all starts with the data you make available to store at these data centers. Each center has clusters of computers and large Internet pipelines to connect the machines to the rest of the world. Each company typically has several of these centers around the world, helping to meet growing demand for its services and guard against service disruptions should one site fail.