. >> kroft: the programmable logic controller, or plc, is one of the most critical pieces of technologyver heard of. they contain circuitry and software essential for modern life, and control the machines that run traffic lights, assembly lines, oil and gas pipelines, not to mention water treatment facilities, electric companies, and nuclear power plants. >> Ó murchú: and that was very worrying to us, because we thought it could've been a water treatment facility here in the u.s., or it could've been trying to take down electricity plants here in the u.s. >> kroft: the first breakthrough came when Ó murchÚ and his five- man team discovered that stuxnet was programmed to collect information every time it infected a computer, and to send it on to two web sites in denmark and malaysia. both had been registered with a stolen credit card, and the operators were nowhere to be found, but Ó murchÚ was able to monitor the communications. >> Ó murchú: well, the first thing we did was we looked at where the infections were occurring in the world and we mapped them out. and that's what we see here.