Kommentare zu: Rasterfahndung: Wildes Rastern bringt nichts http://netzpolitik.org/2007/rasterfahndung-wildes-rastern-bringt-nichts/ Politik in der digitalen Gesellschaft Tue, 14 Oct 2008 06:04:29 +0000 http://wordpress.org/?v=2.5.1 Von: erlehmann http://netzpolitik.org/2007/rasterfahndung-wildes-rastern-bringt-nichts/#comment-123274 erlehmann Thu, 04 Oct 2007 14:46:48 +0000 http://netzpolitik.org/2007/rasterfahndung-wildes-rastern-bringt-nichts/#comment-123274 s/RSdabei/Rasterfahndung bei großer Grundmenge bitte korrigieren, fall möglich. s/RSdabei/Rasterfahndung bei großer Grundmenge

bitte korrigieren, fall möglich.

]]> Von: erlehmann http://netzpolitik.org/2007/rasterfahndung-wildes-rastern-bringt-nichts/#comment-123273 erlehmann Thu, 04 Oct 2007 14:43:35 +0000 http://netzpolitik.org/2007/rasterfahndung-wildes-rastern-bringt-nichts/#comment-123273 Bruce Schneier beschreibt die generelle mathematische Problematik einer RSdabei ganz gut. Wer ein bisschen in Stochastik aufgepasst hat, müsste also folgenden Absatz verstehen. <blockquote> Let's look at some numbers. We'll be optimistic. We'll assume the system has a 1 in 100 false positive rate (99% accurate), and a 1 in 1,000 false negative rate (99.9% accurate). Assume one trillion possible indicators to sift through: that's about ten events -- e-mails, phone calls, purchases, web surfings, whatever -- per person in the U.S. per day. Also assume that 10 of them are actually terrorists plotting. This unrealistically-accurate system will generate one billion false alarms for every real terrorist plot it uncovers. Every day of every year, the police will have to investigate 27 million potential plots in order to find the one real terrorist plot per month. Raise that false-positive accuracy to an absurd 99.9999% and you're still chasing 2,750 false alarms per day -- but that will inevitably raise your false negatives, and you're going to miss some of those ten real plots. <a href="http://www.schneier.com/blog/archives/2006/03/data_mining_for.html" rel="nofollow">Quelle</a></blockquote> Bruce Schneier beschreibt die generelle mathematische Problematik einer RSdabei ganz gut. Wer ein bisschen in Stochastik aufgepasst hat, müsste also folgenden Absatz verstehen.

Let’s look at some numbers. We’ll be optimistic. We’ll assume the system has a 1 in 100 false positive rate (99% accurate), and a 1 in 1,000 false negative rate (99.9% accurate).

Assume one trillion possible indicators to sift through: that’s about ten events — e-mails, phone calls, purchases, web surfings, whatever — per person in the U.S. per day. Also assume that 10 of them are actually terrorists plotting.

This unrealistically-accurate system will generate one billion false alarms for every real terrorist plot it uncovers. Every day of every year, the police will have to investigate 27 million potential plots in order to find the one real terrorist plot per month. Raise that false-positive accuracy to an absurd 99.9999% and you’re still chasing 2,750 false alarms per day — but that will inevitably raise your false negatives, and you’re going to miss some of those ten real plots.

Quelle

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