He said: ”I suspect Russia will choose not to respond in military terms. But cyber warfare is highly likely.
“It will be an attack on national infrastructure, not just upsetting city firms, but getting inside the transport system, or the health system, or air traffic control. It could affect everyone.”
The UK, US and France launched 105 missiles at suspected chemical weapons sites in three strikes in Damascus and near Homs on Saturday.
Will Russia launch CYBER warfare?
Boris Johnson has warned Britain needs to take “very possible precaution” to protect itself against possible Russian cyber attacks”.
Speaking on the BBC’s Andrew Marr Show on Sunday, the UK foreign secretary said relations between both countries had declined with the poisoning of Sergei and Yulia Skripal, and Saturday’s missile air strikes in Damascus and Homs.
Commenting on whether he was worried about revenge cyber attacks on the NHS and electrical facilities, Mr Johnson said: “I think we have to take every possible precaution.
And when you look at what Russia has done, not just in this country, in Salisbury, attacks on TV stations, on the democratic processes, on critical national infrastructure – of course we have to be very, very cautious indeed.”
The Foreign Secretary said there was evidence Moscow had carried out cyber attacks targeting national infrastructure before.
Ministry of Defence officers and the Government Communication Headquarters (GCHQ) are now said to be on high alert for possible cyber warfare.
The NHS has proven to be a weak target for cyber attacks in the past.
In 2017, more than a third of health trusts in England were targeted by the WannaCry ransomware, leading to the cancellation of 6,900 appointments.
It was the NHS’s biggest cyber attack to date.
Why would the UK be at risk?
Britain is blamed for its role in Saturday’s attacks, with the Royal Air Force confirming four of its Tornado GR4s were used in an assault at a base 15 miles west of Homs.
Theresa May said the UK had to act to prevent the use of chemical weapon warfare becoming normalised.
She said: “I have taken this decision because I believe it is the right thing to do. I believe it is absolutely in our national interest.”
Presidents Assad and Putin have both dismissed reports of a chemical attack in Syria, which led to Saturday’s air assault.
A senior Russian military official said 71 of the missiles were intercepted but the Pentagon called the mission a success.