Such an instance has recently been remarked on by The Washingtonian's Shane Harris, and concerns an e-mail spear-phishing attempt thought to have been orchestrated and executed by Chinese spies.
It happened back in 2009, when the US was conducting negotiations with China regarding a possible reduction of greenhouse-gas emissions. At the time, five State Department employees who were involved in the negotiations have received e-mails purportedly coming from National Journal’s columnist and editor Bruce Stokes.
Titled "China and Climate Change” and containing relevant comments, the e-mails seemed like a legitimate request for a comment from a well-known journalist who also has various connections to the diplomatic corps.
Unfortunately for the targets, the messages weren't sent by Stokes, and contained attachments with malware that would open a backdoor on the recipients' computer and allow intruders to remotely access it and retrieve files from it.
But whether the attack succeeded or not, the cable doesn't say. It also doesn't say that the Chinese are behind it, only that it happened while the negotiations were in process.
And the attack would have remained a secret for everyone at National Journal where it not for the fact that the son of one of its editors read the cable and wrote “I see that the Chinese government is using your magazine as a tool for international espionage,” in an e-mail to his father.