In the Petraeus saga, though, the country's top intelligence officer was betrayed by metadata, seemingly anonymous recordings that internet companies make of when and where someone logged into an email account, a facebook profile or the like. While the FBI was monitoring an email account that was reportedly the source of some harassing emails, it found a series of IP addresses recorded when a user logged in from hotel WiFi networks. By cross-referencing those logins with hotel guest lists, the agency ascertained that Broadwell was the only one who could have logged in.
A second account, in which Broadwell and Petraeus corresponded about their affair by saving messages in the "drafts" folder, was also linked to Broadwell in this way. Ian Goldberg, a computer scientist at the University of Waterloo in Ontario, says the important thing to learn from the Petraeus affair is that metadata is at least as, if not more, important than the content of the emails themselves.