'm going to start with three data points. One: Some of the Chinese military hackers who were implicated in a broad set of attacks against the U.S. government and corporations were identified because they accessed Facebook from the same network infrastructure they used to carry out their attacks.
Two: Hector Monsegur, one of the leaders of the LulzSac hacker movement, was identified and arrested last year by the FBI. Although he practiced good computer security and used an anonymous relay service to protect his identity, he slipped up.

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