UK at risk of cyber-warfare

“As EU governments discuss ways in which they can toughen up sanctions against Russia today, they need to be mindful of the ways in which Russia could retaliate” says Professor Mike Jackson.  
“Traditionally the response to sanctions has been the denial of essential supplies to those imposing the sanctions (for example ceasing to supply oil to Germany). In today’s electronic age the response might be to electronically disrupt the workings of government and industry.
“Over the last few years a group of cyber spies has functioned in Eastern Europe. They are thought to be sponsored by the Russian Government, although this has not been definitely shown to be the case. The group has infiltrated computers in many Western Government departments and major defence companies such as BAE. It is thought that primarily they are fishing for secrets but there is no reason where their networks could not be used to disable IT operations and cripple government functions.
“If Russia is pushed too far will they choose to deploy cyber-warfare?”