Little Brother

I realized she was so angry she couldn't speak.
    "Good bye, Marcus," she said, and got to her feet. Before I knew it, she was walking away so fast she was practically running.
    "Van!" I called, getting to my feet and chasing after her. "Van! Wait!"
    She picked up speed, making me run to catch up with her.
    "Van, what the hell," I said, catching her arm. She jerked it away so hard I punched myself in the face.
    "You're psycho, Marcus. You're going to put all your little Xnet buddies in danger for their lives, and on top of it, you're going to turn the whole city into terrorism suspects. Can't you stop before you hurt these people?"
    I opened and closed my mouth a couple times. "Van, I'm not the problem, they are. I'm not arresting people, jailing them, making them disappear. The Department of Homeland Security are the ones doing that. I'm fighting back to make them stop."
    "How, by making it worse?"
    "Maybe it has to get worse to get better, Van. Isn't that what you were saying? If everyone was getting pulled over —"
    "That's not what I meant. I didn't mean you should get everyone arrested. If you want to protest, join the protest movement. Do something positive. Didn't you learn anything from Darryl? Anything? "
    "You're damned right I did," I said, losing my cool. "I learned that they can't be trusted. That if you're not fighting them, you're helping them. That they'll turn the country into a prison if we let them. What did you learn, Van? To be scared all the time, to sit tight and keep your head down and hope you don't get noticed? You think it's going to get better? If we don't do anything, this is as good as it's going to get . It will only get worse and worse from now on. You want to help Darryl? Help me bring them down!"
    There it was again. My vow. Not to get Darryl free, but to bring down the entire DHS. That was crazy, even I knew it. But it was what I planned to do. No question about it.
    Van shoved me hard with both hands. She was strong from school athletics — fencing, lacrosse, field hockey, all the girls-school sports — and I ended up on my ass on the disgusting San Francisco sidewalk. She took off and I didn't follow.

    > The important thing about security systems isn't how they work, it's how they fail.
    That was the first line of my first blog post on Open Revolt, my Xnet site. I was writing as M1k3y, and I was ready to go to war.
    > Maybe all the automatic screening is supposed to catch terrorists. Maybe it will catch a terrorist sooner or later. The problem is that it catches us too, even though we're not doing anything wrong.
    > The more people it catches, the more brittle it gets. If it catches too many people, it dies.
    > Get the idea?
    I pasted in my HOWTO for building a arphid cloner, and some tips for getting close enough to people to read and write their tags. I put my own cloner in the pocket of my vintage black leather motocross jacket with the armored pockets and left for school. I managed to clone six tags between home and Chavez High.
    It was war they wanted. It was war they'd get.

    If you ever decide to do something as stupid as build an automatic terrorism detector, here's a math lesson you need to learn first. It's called "the paradox of the false positive," and it's a doozy.
    Say you have a new disease, called Super-AIDS. Only one in a million people gets Super-AIDS. You develop a test for Super-AIDS that's 99 percent accurate. I mean, 99 percent of the time, it gives the correct result — true if the subject is infected, and false if the subject is healthy. You give the test to a million people.
    One in a million people have Super-AIDS. One in a hundred people that you test will generate a "false positive" — the test will say he has Super-AIDS even though he doesn't. That's what "99 percent accurate" means: one percent wrong.
    What's one percent of one million?
    1,000,000/100 = 10,000
    One in a million people has Super-AIDS. If you test a million random people, you'll probably only find one case of real Super-AIDS. But your test won't identify one person as having Super-AIDS. It will identify 10,000 people as having it.
    Your 99 percent accurate test will perform with 99.99 percent inaccuracy .
    That's the paradox of the false positive. When you try to find something really rare, your test's accuracy has to match the rarity of the thing you're looking for. If you're trying to point at a single pixel on your screen, a sharp pencil is a good pointer: the pencil-tip is a