sent to those employees says, quote, what we have done so far is only a small part of our further plan. please sign your name to object below if you don't want to suffer damage. if you don't, not only you, but your family will be in danger. some computer experts suspect north korea may be trying to attack sony because of an upcoming sony movie, a comedy that depicts an assassination attempt on north korean leader kim jong-un. but that's just one possibility. >> there are parts of this attack and patterns that look like things north korea may have done in the past. that's one possible source. the other thing is to look at hacking groups and sony has had issues with hacking groups before, taking things offline, casting threats toward senior executives. so we have to look at those groups as well. >> reporter: he says it also could be a disgruntled employee inside or outside of the company