One of Britain’s top cyber experts has warned that Russian hackers are able to penetrate the country’s military computers.

Major General Jonathan Shaw, a former head of the UK’s cyber defences security programme, said nothing could be done to stop the attacks, which may lead to top-secret information being read by Vladimir Putin.

The retired officer also claimed he expects 800 British troops to be targeted by Russian cyber attacks when they deploy to Estonia this summer.

The retired general suggested limiting the information stored on military computers

Maj Gen Shaw said: ‘The Russians are past masters at electronic warfare. They will be trying to hack into our systems and we should recognise that total cyber security in unachievable.

‘Essentially we cannot defend ourselves, so it is better to limit the information we store on our military computers.

'Technologically speaking, I’d say the Russians were competing with us but they are ahead of us in heir willingness to test the boundaries.

'They’re not as morally or politically constrained as us.’

In 2007, Estonia suffered a huge cyber attack, but no one was ever found responsible.