with a computer violence called petya pair looigz computers around the planet tonight we're going to what security experts say is a massive point of vulnerability for america, our hospitals. as well as the medical devices implanted in many of our bodies. a recent congressional report says the security of our health care systems is in, quote, critical condition. tonight what two doctors slash hackers are doing about it. thouts of computers around the world frozen. >> you can't read any e-mails. you can't read any files. basically, your computer becomes a brick. >> reporter: an ominous message taking over their screens. "your files are no longer accessible. send $300 worth of bitcoin." >> sometimes if you pay you getter data back. sometimes they just take your money and move on. >> reporter: the global ransomware virus known by some as petya that first took out computer systems in ukraine has now spread to the u.s. among those hit, computers in hospital near pittsburgh. >> she called me and said surgery was canceled because the computers were down. >> reporter: this after just last mon