If IP location details were not protected, the linkage could have been established between Petraeus and Broadwell proving at a minimum the existence of some encrypted correspondence.

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Other tools, such as Maxmind, would help find out the physical location of a particular IP address, he said.

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To join up data points into a context, common identities are required (for example, a web page view can be given a geographical location by joining up the IP address of the page request with that from the IP address in an IP intelligence database).

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