but chris tarbel says server logs are not necessarily comprehensi comprehensive. >> so is it absolutely clear that if the server were breached, there would be a log of it somewhere? >> no. >> so it may be that there's no breach that was recorded, that doesn't mean there was no breach? >> correct. >> but a caution, tarbel session the very nature of guccifer's handy work as a criminal hacker, he's a liar. as for the fbi, no one's saying anything on the record. >> i just interviewed guccifer this morning. >> i can't comment on guccifer. >> he's been extradited to the u.s. in the weeks and months to come? >> i can't comment, sorry. >> and marcel lehel lazar was indeed extradited to the u.s. he was charged with hacking. sources close to the investigation confirm fbi agents escorted him from romania to the united states and say they fully intend to question him about the clinton's server, now that he's in u.s. custody. many officials emphasized to us, investigators have seen nothing so far that substantiates his claim. but the investigation continues. was it your intention to try to affect th

among them, former fbi cyber crime expert chris tarbell who led the successful prosecution of the criminals behind the online black market called silk road. he cautions that hackers like guccifer are notorious liars but still he says he takes these allegations seriously. >> it's plausible. because he did get access to e-mails that allegedly came from that server. each e-mail has a header and that tells you the information and the path of where that e-mail came from. >> and if he's lying? >> that seems silly to me. to go on television and admit to a felony you didn't commit seems a little silly. >> a source with knowledge of the investigation tells nbc the fbi review of the clinton server logs did, in fact, show no evidence of hacking. but tarbell says server logs are not necessarily comprehensive. so, it may be that there is no breach that was recorded? that doesn't mean there was no breach. >> correct. >> a source close to the investigation tells us the fbi escorted him to the u.s. and spoke to him in transit. though tonight, several officials emphasize investigators have seen nothing yet

among them former fbi cyber crime expert chris tarbell who led the successful prosecution of the criminalsind the online black market called silk road. he cautions that hackers like guccifer are notorious liars, but still, he says, he takes these allegations seriously. >> it's plausible because he did get access to e-mails that allegedly came from that server. >> if he's lying? >> that seems silly to me to go on television and admit to a felony you didn't commit seems a little silly. >> reporter: a source with knowledge of the investigation tells nbc an fbi review of the clinton server logs did in fact show no evidence of hacking, but tarbell says server logs are not necessarily comprehensive. >> so it may be that there's no breach that was recorded. that doesn't mean there was no breach? >> correct. >> now, a source close to the investigation tells us the fbis skoer escorted to guccifer to the u.s. and spoke to him in transit. investigators have seen nothing yet that substantiates his claim. the investigation continues and we're told by sources, jose, that the fbi does intend to fully que