There’s something of an open secret in the cybersecurity world: internet service providers quietly give away detailed information about which computer is communicating with another to private businesses, which then sells access to that data to a range of third parties, according to multiple sources in the threat intelligence industry.
The information, known as netflow data, is a useful tool for digital investigators. They can use it to identify servers being used by hackers, or to follow data as it is stolen. But the sale of this information still makes some people nervous because they are concerned about whose hands it may fall into.
Link: How Data Brokers Sell Access to the Backbone of the Internet