caroline mccarthy thank you so much. we have a few more questions in a couple of hours. developments out of new york city, divers found more wreckage and another body in the past hour. we'll talk to an aviation expert about the crash here on "msnbc sunday." h whoa! honey honey honey honey honey! okay... i mean... you can't... this isn't a stove, alright? i mean... what if i just walked into the kitchen and started making a salad? - that'd be weird. - right? i mean, look, there's a technique. - okay... - ( strikes match ) wow. it's okay, everyone. - thanks, hon. - you're welcome. announcer: yep, it's that easy, - with kingsford match light. - ( match strikes ) progressive.ncer: ycall or click today. >>> welcome back to "msnbc sunday." i'm alex witt. we get to the latest on the midair crash between a helicopter and single engine plane over new york city's hudson river. a short time ago a fourth body was pulled from the waters of the hudson. we watched live in the last hour as police divers pulled more wreckage from the water. nine people are presumed dead including five it

caroline mccarthy joins me. do we know how this snapped. >> we do know how it happened. something called a distributed denial of service attack which is basically when you have a hacker who wants to bring down a site server and does so by overwhelming it with data. usually that's accomplished by installing a virus on thousands of unwitting pcs, that turns tell into zombies. when that hacker wants to set them into action, those computers can flood the website servers with data. >> we know that happened. do we know where that happened? the person who was targeted was a professor in georgia. >> an economics professor in georgia was the target of the attacks on thursday. we don't know where the attacks were coming from. there have been ongoing cyber skirmishes between activists on both the russian and georgian sides of that political debate. >> but it doesn't mean that somebody had to be sitting in russia. somebody could be sitting in des moines and doing that. >> it could have been anywhere in the world. it is extremely difficult to track down, security experts say. >> how