http://www.nsa.gov/public_info/_files/speeches_testimonies/2013_08_09_the_nsa_story.pdf里面有这么一段：
According to figures published by a major tech provider, the Internet carries 1,826 Petabytes of information per day. In its foreign intelligence mission, NSA touches about 1.6% of that. However, of the 1.6% of the data, only 0.025% is actually selected for review.
每天拦截接近 30PB 的流量...
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