Ex-hacker: 'It's easy to break into companies like Sony'
19 December 2014 Last updated at 02:53 GMT
The White House has described the cyber attack on Sony Pictures as a serious national security matter.
So just how easy is it to hack into a conglomerate like Sony?
The BBC's Alistair Leithead went to meet Marc Maiffret, a former hacker who is now an internet security expert.