Introduction: Eyes and SpiesImagine you''re a secret agent assigned to track someone. How will you do it? Hide in a doorway across the street from his house and wait for him to emerge? Then you can shadow him as he walks to school, or work, or a friend''s place. You might even slip into a restaurant booth near where he''s eating and eavesdrop on his conversations.Maybe . if you''re pretending to be in a classic detective movie. In real life--21st-century life--there''s no need for all that sneaking around. The person you''re tracking is probably carrying a smartphone, so his phone manufacturer, his Internet provider, and a few app designers all know where he is, every moment of every day. As a government operative, you can request those records directly from the companies.

And snooping around in a restaurant is plain silly. Why not monitor his emails instead? You can use security cameras to track his movements, and scanners to watch his car. Scroll through his tweets to see who''s meeting him, or where he''s heading.You can probably find his address, phone number, and photo online, plus a list of his Facebook friends and maybe even some invitations to local events. You might read about him in a school newspaper article or in a list of sports results. It won''t be hard to paint a picture of his daily life.The ability to easily gather all that information about someone seems a little creepy. But you''re a secret agent on official government business.

You''ll only be searching the Internet for the names of terrorists and criminals. Right?Not necessarily.Because computers can collect billions of items of information about every single one of us, and scan that information for patterns, we''re all being "watched." Yes, governments track us so they can pinpoint terrorism suspects. But lots of other people and organizations are also trying to find out who we are and what we do. Corporations analyze our preferences and habits so they can tailor their advertising. Police forces monitor our movements so they can target crime more effectively. In many cases, we''re even tracking ourselves, then releasing our data to the world.

Some people think that''s fine. After all, there are huge benefits to sharing things over the Internet. We meet new friends through social media, spread information, and exchange viewpoints. We market our music or art. By listing our location, we learn about nearby stores or events. It''s often fun to share things freely and make our thoughts and ideas public.Besides, many people believe that surveillance makes everyone safer.[Security Guard icon]If you''re not doing anything wrong, it doesn''t matter who''s watching.

[Body Text]Is that true?If someone decided to stand on his bed, use his hairbrush as a microphone, and lip-synch to the latest episode of The Voice, would he want people peeking at him through his laptop''s webcam? Probably not! What if a girl texted a friend about her most recent crush? Would she want other people reading that message?Or what about this .Imagine you''re shopping in a posh department store, and you take a selfie posing in a fur coat made from endangered zebralope pelts. You send it to your frenemy, who puts the photo online. Okay, that''s silly, but it''s not world-ending. Unless . 10 or 20 years from now, you decide you''d like to be Minister for the Environment. Or head of the Society for the Prevention of Cruelty to Animals. Then the media finds your old photo on the Internet and reposts it for all to see![Privacy Activist icon]Sometimes, private jokes should stay private, photos should stay in our own personal albums, and our emails should go unread by the wider world.

[Sidebar 0.1]The Creepy LineIn 2010, Eric Schmidt, the CEO of Google, said that his company''s policy was to "get right up to the creepy line and not cross it." For example, you might feel okay about the company keeping track of your Google searches. But what if a Google employee turned up at your door with McDonald''s coupons after you searched "hamburgers"? That would seem invasive.This whole idea raises some questions.* Where exactly is the "creepy line"?* Would everyone draw it in the same place?* Who should decide?The Creepy Line sections throughout this book will ask you to consider where you might set the boundaries, if you ruled the world.[Subhead]Smile--You''re on Camera!The way we act when we know we''re being watched is different from the way we act when we''re alone. Scientists say that when people are in groups, or under surveillance, we tend to conform.

We''re more careful, and more likely to act the way everyone else does. We don''t necessarily experiment with new ideas.Way back in 1791, Jeremy Bentham designed what he thought would be the ideal prison. He called it the panopticon. It was a circular structure built around a central core. The prisoners'' cells lined the outer ring. From the center, the guards could see any prisoner at any time.Jeremy suggested that, because the prisoners had no way of knowing when they were being monitored, they would have to behave at all times as if the guards were watching.

They would then self-reform into model citizens.Jeremy''s prison was never built, but some privacy activists say we now live in a "digital panopticon." As we shop online or post on social media, we know that others are tracking and judging our lives. That "I''m being watched" feeling can affect the way we live and think. We might start to pick and choose what we post in order to project a certain image of ourselves. We might behave more carefully and try to blend in better with our friends. Some people worry that when we know we''re being observed, it can change the events we choose to attend, the causes we champion, or the politicians we support. Imagine you see this story in the news: "Government Spy Caught Posing as Member of Local Environmental Group.

" You might think twice about joining that group, even if you believe in their campaigns.The following pages delve into the ways we''re monitored, from the number of footsteps we take each day, to the fast-food companies we "like" on Facebook, to the things we flush down the toilet. Each chapter asks three simple questions:1. Who''s watching, and why?2. Where is the line between public and private?3. How can you keep your secrets to yourself?.