Three years ago, the world witnessed the worst hack ever seen against oil company Saudi Aramco .

In a matter of hours, 35,000 computers were partially wiped or totally destroyed. Chris Kubecka, a former security advisor to Saudi Aramco, told the tale ahead of her presentation about it Thursday at the Black Hat hacking conference in Las Vegas.

As is the most common method, an IT person opened an email and clicked on a link. That let the hackers in. As it was a holiday, only a few personnel were at work. What they noticed was flickering screens, files disappearing and computers that just shut down.

A group calling itself "Cutting Sword of Justice" claimed responsibility. The group said: "This is a warning to the tyrants of this country and other countries that support such criminal disasters with injustice and oppression."

In a frantic rush, Saudi Aramco's computer technicians ripped cables out of the backs of computer servers at data centers all over the world. Every office was physically unplugged from the Internet to prevent the virus from spreading further.

The company flew IT people around the world to scarf up computer hard drives. In all, they bought 50,000 hard drives.

Kubecka said: "Everyone who bought a computer or hard drive from September 2012 to January 2013 had to pay a slightly higher price for their hard drive."

It took five months before the company could put itself back online.

Source: Money.ccn