Ukraine power 'hack attacks' explained
29 February 2016 Last updated at 13:54 GMT
US investigators have accused Russia-based hackers of being behind an attack that caused blackouts across Ukraine in December.
The team said it was not possible to say whether it was the "Russian government or a well-funded [non-government] team".
However, one of the experts involved in the probe has warned that the UK and other countries could be vulnerable to similar cyber-attacks.