Head of the National Cyber Security Centre Ciaran Martin said the UK had been lucky to so far avoid a ‘category one’ attack crippling infrastructure such as energy or the financial services.
His warning comes after the head of the army said Britain was not immune to a ‘hybrid’ attack that could use conventional and cyber warfare methods.
The most serious cyber attack on the UK to date was the WannaCry ransomware attack on hospitals last May, which was classed as a category two incident because there was no risk to life.
In an interview with The Guardian, Mr Martin said: ‘I think it is a matter of when, not if and we will be fortunate to come to the end of the decade without having to trigger a category one attack.’
Mr Martin said the WannaCry attack, which was blamed on North Korea, had also highlighted the risk of attack where the perpetrator loses control.
‘What we have seen over the past year or so is a shift in North Korean attack motivation from what you might call statecraft – disrupting infrastructure – through to trying to get money through attacks on ransomware, albeit in a way that didn’t pan out the way the attackers wanted it to,’ he said.
Other intrusions have been blamed on Russia, China and Iran, which Mr Martin said may have been intelligence-gathering on infrastructure for potential attacks in the future.
‘What we have seen from Russia thus far against the UK is a series of intrusions for espionage and possible pre-positioning into key sectors but in a more controlled form of attack from others,’ he said.
The UK is also increasing its capabilities to retaliate to a cyber attack, he revealed, adding: ‘Offensive cyber will be an increasing part of the UK’s security toolkit.’