REUTERS•GETTY The group hacked more than 54,000 Twitter accounts

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Details of more than 54,000 Twitter accounts, including passwords, were published last week in what experts have described as a dangerous escalation of the global cyber war. The group calling itself 'cyber caliphate', set up by ISIS member Junaid Hussain, encouraged its followers to seize control of the accounts and use them to spread ISIS propaganda. Victims were forced to defencelessly watch as ISIS rhetoric appeared under their names.

IG Hussain was killed by a coalition air strike in August

The jihadis also posted personal details on the social media platform - including mobile phone numbers of the heads of the CIA, FBI and America's National Security Agency (NSA). Most of those affected are based in Saudi Arabia, but some are feared to be British. One victim, a half-British engineer based in Saudi Arabia said: "I am horrified at how they got hold of my details."

IG Hussain was married to fellow British ISIS member Sally Jones

Hussain, from Birmingham, steered the computer hacking division for the depraved terror regime before he was killed in August by a US drone carrying out a joint operation with Britain. Since the extremist's death the hacking group - which briefly hacked a Pentagon Twitter account earlier this year - appeared to keep a low profile. But after spending months reportedly gathering data, it reappeared on Twitter last Sunday declaring: "We are back."

We will raise our flag in the heart of Europe Cyber Caliphate

The group also taunted the West before tweeting a link to the database of stolen Twitter accounts. It said: "We need years to publish what we have. "We will raise our flag in the heart of Europe."

GETTY The group hacked a Pentagon-controlled Twitter account in January

The account was quickly suspended by Twitter - who are believed to have been contacted by a security agency. Cyber security expert Tony McDowell warned: "It is very worrying that terrorists are gathering data in this way."