Despite mounting calls to permit such reviews, FBI officials maintain that disclosing the software's source code would allow hackers to find ways to defeat the system. The officials also argue that such a disclosure could violate copyright protections because Carnivore includes portions of software code from a product licensed to the government by an unidentified vendor.
Congress is expected to press senior FBI officials on the subject at a hearing Monday before a House Judiciary Committee panel led by Florida Republican Rep. Charles T. Canady. Lawmakers have indicated that they would seek assurances from the bureau that e-mails from innocent citizens aren't gobbled up whenever a federal judge agrees that the FBI can plug Carnivore into an Internet service provider's network.
One scheduled witness for the hearing, Matthew Blaze, an AT&T Corp. (T) researcher, says the FBI's failure to fully disclose how Carnivore works has contributed to an "atmosphere of mistrust and confusion."
In an essay published on the Internet last week, Blaze wrote that releasing the system's source code "is a critical first step in assuring the public that Carnivore can at least be configured to do what it is supposed to do." Blaze questioned Carnivore's effectiveness, suggesting that even modest electronic forgery or data-scrambling techniques could foil it, and described conditions under which it could mistakenly capture e-mails and other communications intended for innocent users.
While the FBI is resisting calls for broad disclosure of the source code -- already the target of at least two requests under the Freedom of Information Act -- the bureau has sought to assuage fears by describing in remarkable detail how the system works. On Friday, dozens of reporters crowded a conference room at FBI headquarters to watch a demonstration.
The bureau has also proposed a compromise, tentatively agreeing to an examination of Carnivore by university researchers who would promise not to disclose its blueprints.
The American Civil Liberties Union, one of the groups that has requested the source code, said it might agree to such an offer, if the FBI gives the blueprints to the ACLU and lets it select the experts.