ISIS is using the PlayStation 4 network to recruit and plan attacks because it's 'more secure than WhatsApp', intelligence experts warn, as special forces are deployed on the streets of London with Britain on terror alert.
The move is the biggest security response since the 2005 London bombings and comes after the sickening attacks in Paris on Friday night - the deadliest in Europe since the Madrid bombings in 2004 - that left at least 129 people dead.
In Belgium, which appears to be at the heart of the terror plot, officials believe that terrorists are using consoles to communicate.
Belgian Minister of Home Affairs Jan Jambon said intelligence agencies have discovered evidence of jihadis using the games consoles to communicate with a special, hidden recruitment channel.
He told HNL.be: ’Playstation 4 is even more difficult to monitor than WhatsApp.’
ISIS fanatics are also said to be using a 'cyber caliphate' - protected by their own encryption software - where they plan their next attacks.
Meanwhile, special forces have been deployed to some of the capital's landmarks and busiest spots in the aftermath of the Paris atrocities.
Eighty-nine people were killed after gunmen burst into the Bataclan concert hall and took hostages before security forces stormed the hall.
People were shot dead at restaurants and bars at five other sites in Paris. At least 352 people were injured, of which 99 are critical. ISIS has claimed responsibility.
A security expert has said the government is 'two or three steps' behind ISIS terrorists who are using encrypted computer software and 'burning' messages to avoid detection.
Large numbers of ISIS fighters are young, highly educated Westerners who are fighting the holy war with sophisticated backgrounds and training with digital technology.
Militants' use of Twitter and Facebook allows them to target an entire new generation of young possible recruits, while the beheading videos of James Foley and Steven Sotloff were created using skilled video and audio editing techniques.
Security Expert Will Geddes told MailOnline: 'They are using various different encrypted messaging apps [such as Kik, Surespot, Wickr and Telegram] that cannot be hacked even by secret services.
'The messages they send also have a burn time which means they will be deleted after a certain time so will not show up on a phone.
'This allows them to remain under the threshold of detection and it's becoming increasingly difficult for security services.
'Security services have to get permission from the app if they want to access the data, but many of the apps have an obligation where they need to notify the user that a request for communication has been made.
'This gives them a heads up and they can then move to another app. We are two or three steps behind them.'
He added: 'These messages will include details of the planning stage but then, more critically, when they are at the last stage in preparations for attack and seeing whether everyone is in position.'
The Investigatory Powers Bill, which was published in draft form a fortnight ago by Home Secretary Theresa May, will force internet firms to hand over to MI5, MI6 and GCHQ messages sent on apps and other encrypted services.
The escalating threat posed by ISIS was highlighted in a speech last month by MI5 chief Andrew Parker who warned the group wanted their attacks to kill a maximum number of people.
In a rare public speech he said: 'We have seen greater ambition for mass casualty attacks. All of this underlines the growing threat we face.'
He added: 'It may not yet have reached the high water mark, and despite the successes we have had, we can never be confident of stopping everything.'
Charles Farr, director of the Office for Security and Counter-Terrorism, said ISIS was inspiring people in Britain who 'couldn't go' to its territories in Syria or Iraq to stay and 'undertake attacks.'
Mr Farr said the ISIS ideology and call was either to go and 'join the so called Islamic State' or stay and 'undertake attacks if you couldn't go', the Daily Telegraph reported.
He said this was a 'specific, singular and new phenomenon of ISIS,' a form of 'ideological grooming' of young people and a distinct ideological shift from previous Islamist inspirations.
By Thomas Burrows
© Associated Newspapers Ltd.