Email security tricks

Ryan Gallagher has a Slate article about telephone security:

Having an extramarital affair in 2012 is not an easy task if you’re the chief of the world’s most renowned spy agency. To communicate with your mistress you can set up a Gmail account under a pseudonym, even adopt tactics favored by terrorists to avoid email interception. But your digital trail can still be traced—as philandering former CIA director David Petraeus recently discovered.
Just in case you’re reading this after awaking from a coma: Petraeus was caught out having an affair with Paula Broadwell, his biographer, following an FBI investigation into harassing emails allegedly sent by Broadwell using a pseudonym to another woman. The FBI’s cyber-crime unit reportedly traced the emails to Broadwell with the help of Gmail metadata (presumably such as IP addresses) and began monitoring her accounts. While Broadwell was under surveillance, the agents apparently discovered that she and Petraeus were sending each other sexually explicit messages using private Gmail accounts. Petraeus was reportedly using a pseudonym, so the agents did not immediately realize it was him. But eventually, somehow, they made the connection.
Much of what is known remains deeply murky and is still unfolding. However, interesting details about how Petraeus and Broadwell apparently tried to prevent their communications from being picked up are trickling out. Not only were they using pseudonyms, but they were using a method known in the intelligence community as the “dead drop”, a tactic favored by terrorists trying to evade government surveillance of communications networks. Before the Internet, dead drops, often used by spies, would involve hiding a written message or package in a secret location or letterbox that only your fellow operatives would know about. According to a revealing AP report quoting an anonymous US official yesterday, Petraeus and Broadwell used a higher-tech version of the dead-drop technique: “Rather than transmitting emails to the other's inbox, they composed at least some messages and instead of transmitting them, left them in a draft folder or in an electronic ‘dropbox’, the official said. Then the other person could log onto the same account and read the draft emails there. This avoids creating an email trail that is easier to trace.”
But Petraeus, as a spy chief, should probably have known better. Using the dead-drop tactic can certainly reduce the chances that sweeping surveillance dragnets will gobble up your communications— but it is not exactly secure. The method was used by the planners of the Madrid train bombings in 2004, which killed 191 people, helping them to operate below the radar of Big Brother. However, law enforcement agencies over the years have grown accustomed to terrorists using the dead drop, and technologies have been developed to help counter it.
An interception tool developed by the networking company Zimbra, for instance, was specifically designed to help combat email dead drops. Zimbra’s “legal Intercept” technology allows law enforcement agencies to obtain “copies of email messages that are sent, received, or saved as drafts from targeted accounts.” An account that is under surveillance, with the help of Zimbra’s technology, will secretly forward all of its messages, including drafts, to a “shadow account” used by law enforcement. This may have been how the FBI was able to keep track of all correspondence being exchanged between Petraeus and Broadwell.
(It’s also worth noting that archived draft emails stored alongside sent and received messages on Google’s servers can actually be obtained by law enforcement with very little effort. Due to the outdated Electronic and Communications and Privacy Act, any content stored in the cloud can be obtained by the government without a warrant if it’s older than six months, as Wired reported last year.)
What this means is that, if Petraeus and Broadwell had been savvy enough to use encryption and anonymity tools, their affair would probably never have been exposed. If they had taken advantage of PGP encryption, the FBI would have been able to decipher their randy interactions only after deploying Trojan-style spyware onto Broadwell’s computer. Further still, if the lovers had only ever logged into their pseudonymous Gmail accounts using anonymity tools like Tor, their real IP addresses would have been masked and their identities extremely difficult to uncover.
But, then, it is unlikely that they ever expected to come under FBI surveillance. Their crime was a moral one, not a felony, so there was no real reason to take extra precautions. In any other adulterous relationship a pseudonym and a dead drop would be more than enough to keep it clandestine, as my Slate colleague Farhad Manjoo noted in an email.
Broadwell slipped up when she sent the harassing emails— as that, as far as we know, is what ended up exposing her and Petraeus to surveillance. Whether the harassment was serious enough to merit email monitoring is still to be established, as Emily Bazelon writes on XX Factor. It goes without saying, however, that the real error here was ultimately made by Petraeus. If he had stayed faithful to his wife of 38 years in the first place, he’d still be in charge at the CIA— and I wouldn’t be writing about how he could have kept his adultery secret more effectively by using encryption.

Rico says he'd been wondering the same thing; how smart a CIA director could Petraeus have been if he didn't know how to do this better? (Or ask some thirteen-year-old how to do it?)