Even after the recent scrutiny of the National Security Agency's domestic surveillance project approved by President Bush, an intriguing question remains unanswered: Which corporations cooperated with the spy agency?

Some reports have identified executives at "major telecommunications companies" who chose to open their networks to the NSA. Because it may be illegal to divulge customer communications, though, not one has chosen to make its cooperation public.

Under federal law, any person or company who helps someone "intercept any wire, oral, or electronic communication" --unless specifically authorized by law--could face criminal charges. Even if cooperation is found to be legal, however, it could be embarrassing to acknowledge opening up customers' communications to a spy agency.

A survey by CNET News.com has identified 15 large telecommunications and Internet companies that are willing to say that they have not participated in the NSA program, which intercepts e-mail and telephone calls without a judge's approval.

Twelve other companies that were contacted and asked identical questions chose not to reply, in some cases citing "national security" as the reason.

Those results come amid a push on Capitol Hill for more information about the NSA's wiretapping practices. On Monday, Attorney General Alberto Gonzales is expected to testify at a Senate Judiciary Committee hearing, and President Bush and his closest allies have been stepping up their defense of the program in preparation for it.

To be sure, there are a number of possible explanations for the companies' silence. In some cases, a company's media department could have been overworked. Another possibility is the company's lawyers were unavailable or chose not to reply for unknown reasons.

Also, some survey recipients, such as NTT Communications, responded with a general statement expressing compliance "with law enforcement requests as permitted and required by law" rather than addressing the question of NSA surveillance.

A lawsuit that could yield more details about industry cooperation is winding its way through the federal courts. Last week, the Electronic Frontier Foundation, a civil liberties group based in San Francisco, sued AT&T after a report that the company had shared its customer records database--though not its network--with the NSA.

AT&T would not respond when asked whether it participated. An AT&T spokesman, Dave Pacholczyk, said: "We don't comment on matters of national security."

The News.com survey, started Jan. 25, found that wireless providers and cable companies were the most likely to distance themselves from the NSA. Cingular Wireless, Comcast, Cox Communications, Sprint Nextel and T-Mobile said they had not turned over information or opened their networks to the NSA without being required by law.

Companies that are backbone providers, or which operate undersea cables spanning the ocean, were among the least likely to respond. AT&T, Cable & Wireless, Global Crossing, Level 3, NTT Communications, SAVVIS Communications and Verizon Communications chose not to answer the questions posed to them.

The New York Times reported on Dec. 24 that the NSA has gained access to switches that act as gateways at the borders between the United States' communications networks and international networks. But "the identities of the corporations involved could not be determined," the newspaper added.

At the water's edge
Analysts and historians who follow the intelligence community have long said the companies that operate submarine cables--armored sheaths wrapped around bundles of fiber optic lines--surreptitiously provide access to the NSA.

"You go to Global Crossing and say...once your cable comes up for air in New Jersey or on the coast of Virginia, wherever it goes up, we want to put a little splice in, thank you very much, which NSA can do," said Matthew Aid, who recently completed the first volume in a multiple-volume history of the NSA. "The technology of getting access to that stuff is fairly straightforward."

Aid was citing Global Crossing as an example, not singling it out. Global Crossing describes itself as an Internet backbone network that shuttles traffic for about 700 telecommunications carriers, mobile operators and Internet service providers. According to the International Cable Protection Committee, the company has full or partial ownership of several trans-Atlantic and trans-Pacific cables.

Global Crossing spokesman Tom Topalian said "99 percent of wiretapping is done at a local phone company level" instead of at backbone providers. Topalian declined to answer questions about NSA access, and added: "All U.S. carriers have to comply with the CALEA act, and Global Crossing complies with CALEA." (CALEA is a 1994 federal law requiring certain telecommunications providers to make their networks wiretap-friendly for domestic law enforcement, not intelligence agencies.)

Rep. John Conyers, D-Mich., last month sent a letter (click for PDF) to companies including Google, Yahoo, EarthLink, Verizon and T-Mobile asking them if they cooperated with the NSA. News.com asked similar questions, but expanded the number of companies to include backbone and submarine cable providers.

Among the companies that responded, some offered far more detail than others. Les Seagraves, EarthLink's chief privacy officer, said: "We've never even been asked to give information without the benefit of a subpoena or a court order behind it. And our policy is to require a subpoena or court order, basically to require a court of law behind the inquiry."

"We're very interested in protecting our customers' privacy and balancing that with our duties to comply with the law," Seagraves added. "Our way to balance that is to definitely make sure we have a valid legal request before we release any information."

Comcast spokesman Tim Fitzpatrick said the company "will only provide customer information pursuant to a valid court order and only if Comcast's records contain information sufficient to identify the customer account on the (date or dates) listed in the court order."

A representative of Cox Communications, David Grabert, said: "Cox has never received a request for information or a wiretap that was not accompanied by a warrant."

NSA's history of industry deals
Louis Tordella, the longest-serving deputy director of the NSA, acknowledged to overseeing a similar project to intercept telegrams as recently as the 1970s. It relied on the major telegraph companies including Western Union secretly turning over copies of all messages sent to or from the United States.

"All of the big international carriers were involved, but none of 'em ever got a nickel for what they did," Tordella said before his death in 1996, according to a history written by L. Britt Snider, a Senate aide who became the CIA's inspector general.

The telegraph interception operation was called Project Shamrock. It involved a courier making daily trips from the NSA's headquarters in Fort Meade, Md., to New York to retrieve digital copies of the telegrams on magnetic tape.

Like today's eavesdropping system authorized by Bush, Project Shamrock had a "watch list" of people in the U.S. whose conversations would be identified and plucked out of the ether by NSA computers. It was intended to be used for foreign intelligence purposes.

Then-President Richard Nixon, plagued by anti-Vietnam protests and worried about foreign influence, ordered that Project Shamrock's electronic ear be turned inward to eavesdrop on American citizens. In 1969, Nixon met with the heads of the NSA, CIA and FBI and authorized a program to intercept "the communications of U.S. citizens using international facilities," meaning international calls, according to James Bamford's 2001 book titled "Body of Secrets."

Nixon later withdrew the formal authorization, but informally, police and intelligence agencies kept adding names to the watch list. At its peak, 600 American citizens appeared on the list, including singer Joan Baez, pediatrician Benjamin Spock, actress Jane Fonda and the Rev. Martin Luther King Jr.

Details about Project Shamrock became public as part of a Senate investigation of the NSA. Telegraph companies participating in the program initially balked when questioned by Senate investigators. But documents turned over by the NSA "cast doubt on the veracity of the companies' claims that they could find no documentation pertaining to Shamrock," wrote Snider. "After all, this had concerned the highest levels of their corporate management for at least four years."

Another apparent example of NSA and industry cooperation became public in 1995. The Baltimore Sun reported that for decades NSA had rigged the encryption products of Crypto AG, a Swiss firm, so U.S. eavesdroppers could easily break their codes.

The six-part story, based on interviews with former employees and company documents, said Crypto AG sold its compromised security products to some 120 countries, including prime U.S. intelligence targets such as Iran, Iraq, Libya and Yugoslavia. (Crypto AG disputed the allegations.)

"Only a very few top executives"
The extent of the NSA's surveillance project in operation today remains unclear. Attorney General Gonzales has stressed that the program intercepts e-mail and phone conversations only when "one party to the communication is outside the United States."

In his book titled "State of War," New York Times reporter James Risen wrote: "The NSA has extremely close relationships with both the telecommunications and computer industries, according to several government officials. Only a very few top executives in each corporation are aware of such relationships."

Tapping into undersea copper and fiber-optic cables where they make landfall would be one way to create a virtual web of surveillance that can snare Internet packets or voice communications when they traverse U.S. borders. One benefit for the government is that one participant in the conversation is likely to be overseas--permitting Gonzales and the NSA to stress the interception's international nature.

Another method would be to seek the cooperation of backbone providers with networks entirely within the United States. That could be done with a tap hooked up to the switches at a telephone company or backbone provider, said Phill Shade, a network engineer for WildPackets who is the company's director of international support services. WildPackets sells network analysis software.

"The tap essentially splits off a copy of the traffic--it would literally take a copy of all the traffic as it moves through the wire," Shade said. "Picture a capital letter 'Y' in your head...One copy goes back out the regular wire on the right side of the wire, and the copy you're interested in splitting goes off the left side of the Y to you. These are very common networking devices, used in networks all over the world."

The tap's exact location may matter. Sen. Arlen Specter, a Pennsylvania Republican who is convening Monday's hearing, has asked Gonzales to respond to a series of questions about the legality of the program. One question Specter is posing: If intercepted calls are "routed through switches which were physically located on U.S. soil, would that constitute a violation of law or regulation restricting NSA from conducting surveillance inside the United States?"

The secret electronic wiretapping by the National Security Agency was put in place to intercept terrorist communications, but provoked a storm of opposition from civil libertarians who say the program violates Americans' privacy rights.

The White House about-face came after a leading House Republican whose subcommittee oversees the National Security Agency called for a full congressional inquiry into the domestic spying program.

Republican Representative Heather Wilson of New Mexico, who chairs the House Subcommittee on Technical and Tactical Intelligence, said said she was pleased that the George W. Bush administration had reconsidered it position.

"The checks and balances in our system of government are very important, and it's those checks and balances that are going on and are being executed now," Wilson said at a press conference Wednesday.

"I had serious concerns and questions about this program when it was initially reported," she said. "We must conduct a complete review of this program.

In a statement, House Intelligence Committee Chairman Peter Hoekstra called the briefing "a positive first step."

"I appreciate the White House's willingness to inform more members on aspects of this vital NSA program," he said.

Meanwhile, Republican US Senator Arlen Specter said on the floor of the Senate that he soon would introduce legislation requiring the White House to seek approval from a special federal court in order to continue the eavesdropping program.

"The thrust of the legislative proposal that I am drafting ... is to require the administration to take the program to the Foreign Intelligence Surveillance Court," said Specter, chairman of the powerful Senate Judiciary Committee, which held hearings into the legality of the program earlier this week.

"We want to be secure and we want to have the military -- and the administration and the president -- have all the tools he needs to fight terrorism, but we also want to maintain our civil liberties," he said.

"What is involved is the equilibrium of the constituional system, and that's a very weighty concept," Specter said.

The two heads of the Foreign Intelligence Surveillance Court were the only judges in the country briefed by the administration on Bush's program. The president's secret order, issued sometime after the Sept. 11, 2001, attacks, allows the National Security Agency to monitor telephone calls and e-mails between people in the United States and contacts overseas.

James A. Baker, the counsel for intelligence policy in the Justice Department's Office of Intelligence Policy and Review, discovered in 2004 that the government's failure to share information about its spying program had rendered useless a federal screening system that the judges had insisted upon to shield the court from tainted information. He alerted Kollar-Kotelly, who complained to Justice, prompting a temporary suspension of the NSA spying program, the sources said.

Yet another problem in a 2005 warrant application prompted Kollar-Kotelly to issue a stern order to government lawyers to create a better firewall or face more difficulty obtaining warrants.

The two judges' discomfort with the NSA spying program was previously known. But this new account reveals the depth of their doubts about its legality and their behind-the-scenes efforts to protect the court from what they considered potentially tainted evidence. The new accounts also show the degree to which Baker, a top intelligence expert at Justice, shared their reservations and aided the judges.

Both judges expressed concern to senior officials that the president's program, if ever made public and challenged in court, ran a significant risk of being declared unconstitutional, according to sources familiar with their actions. Yet the judges believed they did not have the authority to rule on the president's power to order the eavesdropping, government sources said, and focused instead on protecting the integrity of the FISA process.

It was an odd position for the presiding judges of the FISA court, the secret panel created in 1978 in response to a public outcry over warrantless domestic spying by J. Edgar Hoover's FBI. The court's appointees, chosen by then-Chief Justice William H. Rehnquist, were generally veteran jurists with a pro-government bent, and their classified work is considered a powerful tool for catching spies and terrorists.

The FISA court secretly grants warrants for wiretaps, telephone record traces and physical searches to the Justice Department, whose lawyers must show they have probable cause to believe that a person in the United States is the agent of a foreign power or government. Between 1979 and 2004, it approved 18,748 warrants and rejected five.

Lamberth, the presiding judge at the time of the Sept. 11 attacks, and Kollar-Kotelly, who took over in May 2002, have repeatedly declined to comment on the program or their efforts to protect the FISA court. A Justice Department spokesman also declined to comment.

Both presiding judges agreed not to disclose the secret program to the 10 other FISA judges, who routinely handled some of the government's most highly classified secrets.

So early in 2002, the wary court and government lawyers developed a compromise. Any case in which the government listened to someone's calls without a warrant, and later developed information to seek a FISA warrant for that same suspect, was to be carefully "tagged" as having involved some NSA information. Generally, there were fewer than 10 cases each year, the sources said.

According to government officials familiar with the program, the presiding FISA judges insisted that information obtained through NSA surveillance not form the basis for obtaining a warrant and that, instead, independently gathered information provide the justification for FISA monitoring in such cases. They also insisted that these cases be presented only to the presiding judge.

Lamberth and Kollar-Kotelly derived significant comfort from the trust they had in Baker, the government's liaison to the FISA court. He was a stickler-for-rules career lawyer steeped in foreign intelligence law, and had served as deputy director of the office before becoming the chief in 2001.

Baker also had privately expressed hesitation to his bosses about whether the domestic spying program conflicted with the FISA law, a government official said. Justice higher-ups viewed him as suspect, but they also recognized that he had the judges' confidence and kept him in the pivotal position of obtaining warrants to spy on possible terrorists.

In 2004, Baker warned Kollar-Kotelly he had a problem with the tagging system. He had concluded that the NSA was not providing him with a complete and updated list of the people it had monitored, so Justice could not definitively know -- and could not alert the court -- if it was seeking FISA warrants for people already spied on, government officials said.

Kollar-Kotelly complained to then-Attorney General John D. Ashcroft, and her concerns led to a temporary suspension of the program. The judge required that high-level Justice officials certify the information was complete -- or face possible perjury charges.

In 2005, Baker learned that at least one government application for a FISA warrant probably contained NSA information that was not made clear to the judges, the government officials said. Some administration officials explained to Kollar-Kotelly that a low-level Defense Department employee unfamiliar with court disclosure procedures had made a mistake.

Kollar-Kotelly asked Defense Secretary Donald H. Rumsfeld to ensure that wouldn't happen again, government officials said.

Baker declined to comment through an office assistant, who referred questions about his FISA work to a Justice Department spokesman. Pentagon spokeswoman Cynthia Smith also declined to comment and referred questions to Justice officials. Justice spokesman Brian Roehrkasse said the department could not discuss its work with the FISA court.

"The department always strives to meet the highest ethical and professional standards in its appearances before any court, including the FISA court," Roehrkasse said. "This is especially true when department attorneys appear before a court on an ex parte basis, as is the case in the FISA court."

Shortly after the warrantless eavesdropping program began, then-NSA Director Michael V. Hayden and Ashcroft made clear in private meetings that the president wanted to detect possible terrorist activity before another attack. They also made clear that, in such a broad hunt for suspicious patterns and activities, the government could never meet the FISA court's probable-cause requirement, government officials said.

So it confused the FISA court judges when, in their recent public defense of the program, Hayden and Attorney General Alberto R. Gonzales insisted that NSA analysts do not listen to calls unless they have a reasonable belief that someone with a known link to terrorism is on one end of the call. At a hearing Monday, Gonzales told the Senate Judiciary Committee that the "reasonable belief" standard is merely the "probable cause" standard by another name.

Several FISA judges said they also remain puzzled by Bush's assertion that the court was not "agile" or "nimble" enough to help catch terrorists. The court had routinely approved emergency wiretaps 72 hours after they had begun, as FISA allows, and the court's actions in the days after the Sept. 11 attacks suggested that its judges were hardly unsympathetic to the needs of their nation at war.

On Sept. 12, Bush asked new FBI Director Robert S. Mueller III in a Cabinet meeting whether it was safe for commercial air traffic to resume, according to senior government officials. Mueller had to acknowledge he could not give a reliable assessment.

Mueller and Justice officials went to Lamberth, who agreed that day to expedited procedures to issue FISA warrants for eavesdropping, a government official said.

The requirement for detailed paperwork was greatly eased, allowing the NSA to begin eavesdropping the next day on anyone suspected of a link to al Qaeda, every person who had ever been a member or supporter of militant Islamic groups, and everyone ever linked to a terrorist watch list in the United States or abroad, the official said.

In March 2002, the FBI and Pakistani police arrested Abu Zubaida, then the third-ranking al Qaeda operative, in Pakistan. When agents found Zubaida's laptop computer, a senior law enforcement source said, they discovered that the vast majority of people he had been communicating with were being monitored under FISA warrants or international spying efforts.

"Finally, we got some comfort" that surveillance efforts were working, said a government official familiar with Zubaida's arrest.