In slide made public by the newspapers, NSA analysts were encouraged to use data coming from both Prism and from the fiber-optic cables.
Prism, as its name suggests, helps narrow and focus the stream. If eavesdroppers spot a suspicious email among the torrent of data pouring into the United States, analysts can use information from Internet companies to pinpoint the user.
With Prism, the government gets a user’s entire email inbox. Every email, including contacts with American citizens, becomes government property.
Once the NSA has an inbox, it can search its huge archives for information about everyone with whom the target communicated. All those people can be investigated, too.
That’s one example of how emails belonging to Americans can become swept up in the hunt.
In that way, Prism helps justify specific, potentially personal searches. But it’s the broader operation on the Internet fiber optics cables that actually captures the data, experts agree.
“I’m much more frightened and concerned about real-time monitoring on the Internet backbone,” said Wolf Ruzicka, CEO of EastBanc Technologies, a Washington software company. “I cannot think of anything, outside of a face-to-face conversation, that they could not have access to.”
One unanswered question, according to a former technology executive at one of the companies involved, is whether the government can use the data from Prism to work backward.
For example, not every company archives instant message conversations, chat room exchanges or videoconferences. But if Prism provided general details, known as metadata, about when a user began chatting, could the government “rewind” its copy of the global Internet stream, find the conversation and replay it in full?
That would take enormous computing, storage and code-breaking power. It’s possible the NSA could use supercomputers to decrypt some transmissions, but it’s unlikely it would have the ability to do that in volume. In other words, it would help to know what messages to zero in on.