Yesterday, the New York Times reported that as part of the FBI’s investigation of the Hillary Clinton email scandal, the Bureau is comparing electronic time stamps on classified sources. They hope thereby to figure out whether Clinton aides reviewed the sources and then retyped the information into emails that were sent or forwarded to the Secretary’s private server.

Today, a report from Catherine Herridge and Pamela Browne of Fox News suggests that this is part of an effort to determine how sensitive intelligence “jumped the gap” between the classified systems and Clinton’s unsecured personal server. Herridge and Browne were told that there are several possible ways that classified information got onto Clinton’s server:

Reading intelligence reports or briefings, and then summarizing the findings in emails sent on Clinton’s unsecured personal server. Accessing the classified intelligence computer network, and then lifting sections by typing them verbatim into a device such as an iPad or BlackBerry. Taking pictures of a computer screen to capture the intelligence. Using a thumb drive or disk to physically move the intelligence, but this would require access to a data center. It’s unclear whether Clinton’s former IT specialist Bryan Pagliano, who. . .has reached an immunity deal with the Justice Department, or others had sufficient administrator privileges to physically transfer data.

According to Herridge and Browne, most of these scenarios would require a password. Moreover, all of these practices would be strictly prohibited under non-disclosure agreements signed by Clinton and others, and federal law.

Untangling this mess is made more difficult by the fact that, according to Herridge and Browne, it remains unclear who had access to which computers and devices used by Clinton while she was secretary of state and where exactly they were located at the time of the email correspondence. However, the FBI reportedly has been able to develop a list of individuals who will be questioned about their direct handling of the emails in order to get at the issue of how classified information “jumped the gap.”

The list of individuals is said to be relatively small — about a dozen. The pivotal figure is probably Clinton aide Jake Sullivan because he forwarded so many emails containing highly classified information to Clinton, including one that referred to human spying.

Herridge and Browne say that the investigators working on this part of the inquiry are not political appointees, but rather top notch agents with decades of experience. However, political appointees will make the final determination about whether, and whom, to prosecute.