In the world of hypothetical cybercrime, not much is scarier than the hacked medical device. Compromised pacemakers played a central role last year in an episode of Homeland and provided a macabre sidenote to this year's Black Hat conference for hackers. It wasn't science fiction: There's ample evidence that it's possible to seize control of such implants from a distance. There's just no evidence that's ever happened. Still, regulators and computer security experts are dedicating a fair amount of attention to warding off such threats. On Thursday, the Center for Internet Security, a nonprofit group that advises government agencies and private companies, said it was beginning work on a set of guidelines for medical devices, beginning with insulin pumps.