Inside DCSNet, the FBI's Nationwide Eavesdropping Network

Aug. 28 -- The FBI has quietly built a sophisticated, point-and-click surveillance system that performs instant wiretaps on almost any communications device, according to nearly a thousand pages of restricted documents newly released under the Freedom of Information Act.

The surveillance system, called DCSNet, for Digital Collection System Network, connects FBI wiretapping rooms to switches controlled by traditional land-line operators, internet-telephony providers and cellular companies. It is far more intricately woven into the nation's telecom infrastructure than observers suspected.

It's a "comprehensive wiretap system that intercepts wire-line phones, cellular phones, SMS and push-to-talk systems," says Steven Bellovin, a Columbia University computer science professor and longtime surveillance expert.

DCSNet is a suite of software that collects, sifts and stores phone numbers, phone calls and text messages. The system directly connects FBI wiretapping outposts around the country to a far-reaching private communications network.

Many of the details of the system and its full capabilities were redacted from the documents acquired by the Electronic Frontier Foundation, but they show that DCSNet includes at least three collection components, each running on Windows-based computers.

The $10 million DCS-3000 client, also known as Red Hook, handles pen-registers and trap-and-traces, a type of surveillance that collects signaling information -- primarily the numbers dialed from a telephone -- but no communications content. (Pen registers record outgoing calls; trap-and-traces record incoming calls.)

DCS-6000, known as Digital Storm, captures and collects the content of phone calls and text messages for full wiretap orders.

A third, classified system, called DCS-5000, is used for wiretaps targeting spies or terrorists.

Together, the surveillance systems let FBI agents play back recordings even as they are being captured (like TiVo), create master wiretap files, send digital recordings to translators, track the rough location of targets in real time using cell-tower information, and even stream intercepts outward to mobile surveillance vans.

FBI wiretapping rooms in field offices and undercover locations around the country are connected through a private, encrypted backbone that is separated from the internet. Sprint runs it on the government's behalf.

The network allows an FBI agent in New York, for example, to remotely set up a wiretap on a cell phone based in Sacramento, California, and immediately learn the phone's location, then begin receiving conversations, text messages and voicemail pass codes in New York. With a few keystrokes, the agent can route the recordings to language specialists for translation.

The numbers dialed are automatically sent to FBI analysts trained to interpret phone-call patterns, and are transferred nightly, by external storage devices, to the bureau's Telephone Application Database, where they're subjected to a type of data mining called link analysis.

FBI endpoints on DCSNet have swelled over the years, from 20 "central monitoring plants" at the program's inception, to 57 in 2005, according to undated pages in the released documents. By 2002, those endpoints connected to more than 350 switches.

Today, most carriers maintain their own central hub, called a "mediation switch," that's networked to all the individual switches owned by that carrier, according to the FBI. The FBI's DCS software links to those mediation switches over the internet, likely using an encrypted VPN. Some carriers run the mediation switch themselves, while others pay companies like VeriSign to handle the whole wiretapping process for them.