State-sponsored" hackers stole the details of about 500 million Yahoo users in the largest cyber security breach in history.

Names, email addresses, telephone numbers, dates of birth and encrypted passwords were taken in the 2014 attack, according to Yahoo. However it said credit card data was not stolen.

Sky advised its customers to change their passwords as Yahoo provides the technology behind Sky.com email accounts.

Fellow internet provider BT said a minority of its customers use Yahoo mail services and advised them to change their passwords.

The FBI confirmed it is investigating the alleged breach “by what we believe is a state-sponsored actor".

It declined to name the country it believes carried out the attack.

Reuters reported three unnamed US intelligence officials believe the attack was state-sponsored becauseof its similarity to previous hacks linked to Russian intelligence agencies.

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There have been rumours about such a breach for months while Yahoo was warned that it could have been targeted before it was bought by Verizon for $4.8 billion in August.

Many users have expressed anger on social media that Yahoo did not detect the breach and failed to notify them two months ago when concerns were first raised.

In August a hacker known as ‘Peace’ claimed to be selling details from a Yahoo breach - usernames, passwords and dates of birth from 2012 - for three bitcoins (£1,360).

Yahoo said users should change their passwords if they have not done so since 2014.