In 2008, one Defense Department agency held a conference, and then posted some of the presentation materials online, including the names and email addresses of the 50 or so attendees.

WSJ: Cyberspies Target China Experts in U.S.

The reported incident against a nuclear facility, which the department did not specifically name, was found to be the result of a USB drive that an employee had used to download presentation materials onto a laptop.

CNN: Homeland Security cites sharp rise in cyber attacks

Soon after, the attendees, mostly defense contractors, received emails that purported to be from one of the presenters at the conference and included an attachment that claimed to be his presentation materials, according to a person familiar with the incident.

WSJ: Cyberspies Target China Experts in U.S.