Large chunks of material had been blacked out and Carnivore's source code was missing, said officials at the Electronic Privacy Information Center (EPIC) in Washington.
EPIC recently filed a lawsuit against the FBI for not turning over documents related to the system -- which for counter-terrorism purposes sniffs through e-mail flowing through ISPs, and consequently has created a furore among privacy groups.
But the documents EPIC got hold of did paint a picture of Carnivore's history, noting that the system was originally dubbed Omnivore and got its start in early 1997 on a Solaris X86 computer. In June of last year, the system moved over to the Windows NT platform and became Carnivore.
EPIC also reported that the system has been used to intercept VoIP (voice over IP) data, according to the documents, which also detail performance and recovery incidents.
EPIC vowed to litigate further to get the FBI to turn over missing documents and Carnivore source code. The group claims that about 200 pages were kept entirely out of the material and twice that number of pages had been largely redacted.
EPIC got its hands on this first round of Carnivore material after the FBI was forced by a US judge to comply with the group's Freedom of Information Act (FOIA) request.
FBI officials told US District Judge James Robertson that the agency had 3,000 pages of material which would fall under the EPIC request but FBI officials provided no timeline for handing over that material, said EPIC.