Researchers who found a vulnerability in the protocols used in the Tor anonymous Internet service used it to survey the traffic on the network. They found that “…while the content of Tor hidden services is rather varied, the most popular hidden services are related to botnets.”… Researchers who found a vulnerability in the protocols used in the Tor anonymous Internet service used it to survey the traffic on the network. They found that “…while the content of Tor hidden services is rather varied, the most popular hidden services are related to botnets.”

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