What prevents Carnivore from being used illegally?
The exclusionary rule. This principle in U.S. law states that evidence seized by police in violation of constitutional protection from unreasonable search and seizure may not be used against a criminal defendant at trial. There are some problems with this rule. The first is that exceptions are allowed when evidence is obtained in “good faith” with a search warrant that is later ruled invalid. This means if FBI agents can convince a judge to grant an invalid search warrant, the evidence is still admissible in court. This is a problem because there are subtle privacy issues here that confuse even technologists (and judges are notoriously computer illiterate). For example, a “pen-register” wiretap should only be able to grab the equivalence of call-records, such as the timestamp when the e-mail was sent, the size of the e-mail, and the from/to e-mail addresses. Most technologists would therefore claim that Carnivore should therefore restrict itself to the SMTP “envelope”. However, the FBI
