Former CIA director David Petraeus and his onetime paramour, Paula Broadwell, used the same surreptitious email method to communicate with each other as Canadian spy Sub.-Lt. Jeffrey Delisle did to deliver secrets to his Russian handlers.

Information presented at Delisle's bail hearing and revealed in October after his guilty plea detailed how he would take secrets home on a USB thumbdrive, then access an email account given to him by the Russians and write in drafts.

None of the material was ever transmitted: The Russians would just sign in themselves and read his saved drafts.

In the same way, Petraeus and Broadwell wrote intimate messages as draft emails in a shared Gmail account, allowing them to see one another's messages, but without a trail of internet-protocol (IP) addresses.

Like Delisle, Petraeus and Broadwell were apparently using the trick — known to terrorists and teenagers alike — to conceal their email traffic, a law enforcement official told The Associated Press.

They composed at least some of their messages on Gmail, 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. That avoided creating an email trail that would be much easier to trace.

Broadwell is the 40-year-old married biographer with whom also-married Petraeus had an affair that led to his abrupt resignation Friday from the CIA, in a scandal that now appears to be widening.