If you value your privacy, you should watch out for Carnivore. The dictionary says a carnivore is “any flesh-eating or predatory organism,” but this Carnivore (with a capital “C”) is the FBI’s name for its new secret system to eat your e-mail messages.

The computerized system automatically intercepts messages that contain certain words like “bomb” and “heroin,” although supposedly only messages to or from persons under surveillance. The FBI uses the system to track down drug dealers, as well as likely terrorists and other threats to the national security. But some members of Congress and civil-liberties groups have been making headway lately in raising questions about whether Carnivore goes too far in invading personal privacy.

Under pressure, the FBI has agreed to disclose details of how Carnivore works. The Electronic Privacy Information Center had asked for access to the data under the Freedom of Information Act and had filed a lawsuit to back up its request.

The U.S. Court of Appeals for the District of Columbia has told the Federal Communications Commission that it must clear up its rules on how telephone companies let the FBI intercept communications. The rules now do not distinguish between merely identifying the parties and the content of messages. If the FBI gets the content, privacy advocates say it should be required to get a formal court order. The appeals court told the FCC that it had acted without a “meaningful consideration of privacy” concerns. And Attorney General Janet Reno has ordered a speed-up of studies by a Justice Department team and an as-yet-unnamed university to appraise the impact of Carnivore on privacy rights.

Some people wonder why all the fuss. A talk-show host asked one of the privacy lawyers why anyone should object to Carnivore if he had nothing to hide. The lawyer snapped back: “All right, tell me right now what is your current salary.” The broadcaster, taken aback, said it was “none of your business.” The point was that the FBI, armed with Carnivore, can find out not only your salary but what books you buy, what organizations you support, how big a car you drive, what you paid for your house, what’s in your bank accounts and what debts you owe.

In a related development, The Wall Street Journal has disclosed that the FBI has been demanding that foreign telecommunications firms doing business in the United States hire only U.S. citizens for their operations here, establish their switching operations on U.S. territory, and enable the FBI to spot the location of any telephone it is tapping. The agency is trying to protect its power of surveillance in the face of rapidly changing technology.

Such matters might cause little concern if one could put absolute trust in the fairness and expertise of the FBI. But this is the agency that fingered Martin Luther King as a national security threat and circulated details of his sexual behavior to favored news organizations. It tracked opponents of the war in Vietnam. And more recently, one of its senior agents misled a federal court by testifying falsely that the former Los Alamos nuclear scientist had deceived investigators about his relations with Chinese scientists.

Fortunately, we have our First Amendment freedoms and a court system to enforce them and, in this case, to let the FBI protect the national security without letting overzealous agents invade our privacy.

FBI Director Louis Freeh apparently agrees. He told a House Judiciary subcommittee several years ago that the FBI is “potentially the most dangerous agency in the country if we are not scrutinized properly.”

Mr. Freeh’s spokesman, Bill Carter, verifying that quote, goes on to say that some FBI officials winced at the term Carnivore. But people in their laboratory division had made it up on their own, and it was too late for a change.