In December 1999, U.S. marshals served officials of EarthLink with a court order to install a commercially available device called "EtherPeek," which would be connected to the ISP's Pasadena, Calif., network hub to let the government monitor electronic messages on the system.

Although EarthLink was perfectly willing to abide by the subpoena, company officials were concerned that the device would have the ability to see content and header information for all E-mail messages, which would have been beyond the scope of the court order and an invasion of their customers' privacy.

In an effort to find a compromise, EarthLink's engineers designed software to comply with the court order by giving law enforcement officials the E-mail sender and recipient information--exactly what they had requested--without disclosing their content. The government agreed, reluctantly. "We told the government 'we'll give you the information you request,' but they weren't really happy about it," says Les Seagraves, EarthLink's VP and chief privacy officer.

But several weeks later, government agents insisted on installing their own device. EarthLink filed a motion to quash the original court order. It was during this legal proceeding that the government threw EarthLink a curve. Government officials admitted they weren't going to use off-the-shelf EtherPeek after all. Instead, they planned to use a new, proprietary device with the intimidating name of Carnivore. However, it turned out that Carnivore was incompatible with EarthLink's operating system software and the company was forced to revert to an older version in order to install it.

The result: EarthLink crashed, according to sources familiar with the incident. Exactly when it crashed and for how long and the extent of the damage, if any, that was caused by Carnivore or whether customer E-mails were delayed or lost is unclear because EarthLink and the FBI refuse to discuss the episode. The magistrate's order is sealed from public view, and EarthLink officials won't discuss it. Seagraves will say only, "We have a business relationship with the FBI now. We have our own method to give them what they want."

Legally, Carnivore may one day be at the center of a Constitutional controversy that could reach the Supreme Court. The main argument is that the technology of packet sniffing doesn't allow Carnivore to make absolutely certain that E-mail data not covered by a court order is left unmolested.

Other critics charge that although court orders may allow Carnivore to catch only E-mail addresses of senders and recipients, it also catches additional header information such as message size, how many hops a message takes to reach its destination, time of transmission, and other valuable data that can be extrapolated, giving the FBI information beyond a search warrant's scope.

Last year, the FBI tried to quiet these concerns. It hired an independent group of scientists to test Carnivore and show that it worked as advertised, without exceeding the limits of search warrants. While the intentions were sound, the FBI's plan backfired and spurred controversy. The report, while generally sympathetic to Carnivore's case, pointed out one disturbing shortcoming. "Carnivore reduces but doesn't eliminate risk of both intentional and unintentional unauthorized acquisition of electronic communication information by FBI personnel." It also said that because of the lack of audit trails, FBI agents could snoop on people not listed in the court order and nobody would ever know about it.

This is a technical and legal problem that opponents say could be solved easily if the FBI were willing to publish Carnivore's source code and disclose the essence of how it works. Without knowing how Carnivore does what it does, IT managers are likely to remain wary and suspicious. Plus, those who favor revealing the source code believe that having it available for testing and scrutiny will allow it to perform more precisely in ways that the FBI desires. "The industry says, 'let us see the source code, so we can do it better,'" says EarthLink's Seagraves. But Marcus Thomas, section chief of the FBI's CyberTechnology Section, says the FBI won't reveal the source code because of security concerns. "If we make it public, someone could find ways to subvert it," he says.

Also fueling the controversy are FBI documents that show the agency is planning to update Carnivore to reconstruct Web pages that a subject has viewed as well as listen in on voice-over-Web communications. However, E-mail users and IT managers are likely to take matters into their own hands by using Carnivore-like systems that fit search-warrant requirements exactly and by employing encryption techniques. Opponents worry that local law enforcement agencies will begin using Carnivore; the FBI says local agencies have expressed interest in the device, but that none have employed it. Critics also contend that Carnivore isn't even delivering useful results. Of the estimated 30 deployments, none of the information gleaned by the device has found its way into a courtroom.

The FBI may have one more embarrassing problem to deal with. On the same day the agency decided to change Carnivore's name to DCS-1000, Sachs of Iconn immediately registered the Web domain names http://www.DCS-1000.com, .net and .org. He says he hasn't yet decided what to do with them.