unprecedented in its sheer size, hitting dozens of countries around the world. the victims include fedex in the u.s. and many hospitals in great britain. security experts racing to contain the fallout. bryan llenas joins us live from our new york city newsroom with more details. >> reporter: hi, kelly. hackers used a microsoft windows flaw to launch what appears to be the largest cyber attack of its kind in history on friday. the flaw was leaked online, it was secretly used as a cyber weapon by the u.s. national security agency. hackers exploited this weak point to infect windows computers with ansomeware -- ransomware. it locks your computer, holding your data hostage until a user pays a ransom. this is a screen shot of what the vie russ dubbed wanna cry looked like at a surgery center in northern england friday. this attack is alarming because of the sheer size and speed hitting more than 70 countries including the u.s., u.k., india,