Russian hackers attacked the National Grid
Ciaran Martin, director of cyber security at GCHQ, said the Kremlin-backed hackers also tried to take out telecoms companies such as BT.
They are already believed to have successfully targeted media organisations and brought down websites with denial of service attacks.
Mr Martin will confirm the cyber-attacks, which were designed to bring chaos to across the country, in a statement later today.
The Kremlin-backed cyber-attack on the National Grid could have plunged Britain into darkness
Russian interference has included attacks on the UK media, telecommunication and energy sectors
He is expected to say: "I can't get into precise details of intelligence matters.
"But I can confirm that Russian interference, seen by the National Cyber Security Centre over the past year, has included attacks on the UK media, telecommunication and energy sectors.”
The power grid hack this summer triggered alarms and experts GCHQ were called in to flush out “sleeper” worms.
It is believed the hackers intended to lie dormant inside the energy network after having penetrated it, to then cause significant damage at a later date.
Mr Martin will tell a conference: “Russia is seeking to undermine the international system, that much is clear. The Prime Minister made the point on Monday night – international order as we know it is in danger."
Mr Martin was referring to a speech by Theresa May in which she warned Russian leader Vladimir Putin: "We know what you are doing."
The news comes in the wake of revelations about the role of a small army of Russian Twitter trolls who spread fake news and misinformation via social media.
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A whistleblower told the Mail on Sunday: “We were active on social media, including Twitter, mainly posting on contentious topics obsessing the Brits.”
One Russian account tweeted up to 20 times per hour in English about the vote in the run-up to the Brexit referendum.
Twitter accounts created in Russia were amongst 2,700 handed over to the US House Intelligence Committee as being linked to the Internet Research Agency or the Kremlin’s troll army according to CNN.
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