ISIS fighters, many of them millennials, communicate via encrypted apps

Efforts have been dismissed by jihadists, who called them 'idiots'

ISIS militants have hit back at hacking collective Anonymous' attempts at declaring a cyber war, branding them 'idiots'.

The hacking group promised to hunt down militant jihadists online following the terrorist attacks in Paris last week which left 129 people dead.

However, ISIS jihadists, who use a number of encrypted apps an internet services to communicate and use social media under the radar, are clearly unimpressed with Anonymous' efforts.

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'Idiots': Anonymous declared cyber war on ISIS last week, but the jihadist group are clearly unimpressed with the hacktivists' efforts

In response to the declaration of war, ISIS affiliate the Islamic Cyber Army took to encrypted smartphone-messaging app Telegram to dismiss Anonymous as 'idiots'.

'What they gonna hack…all they can do is hacking twitter accounts, emails, etc…,' the Islamic Cyber Army wrote according to New York Magazine.

'Do not make your email same as your username on twitter this mistake cost many ansar [users sympathetic to ISIS] their accounts and the kuffar [non-Muslims] published their IP, so be careful.'

Anonymous' declaration of war came in a video posted on the group's French YouTube page shortly after the Paris attacks, were they warned the terror group to 'expect us', vowing to hunt down those responsible online and expose them.

Wearing the group's signature Guy Fawkes mask, a spokesman says in French: 'Anonymous from all over the world will hunt you down.

'You should know that we will find you and we will not let you go. We will launch the biggest operation ever against you. Expect massive cyber attacks. War is declared. Get prepared.'

Hitting back: ISIS affiliate the Islamic Cyber Army dismissed hacking collective Anonymous as 'idiots', saying 'all they can do is hacking twitter accounts, emails'

Anonymous already publish and update a list of Twitter accounts they claim spread propaganda in support of ISIS, a list which has now increased to 5,500.

However, as supporters and detractors of ISIS alike have pointed out that jihadists simply have to set up new accounts when their Twitter is shut down or exposed.

ISIS militants use a number of encrypted messaging services, email providers, and GPS blockers to communicate under the radar.

The list of apps used by the jihadists have been revealed after a 34-page ISIS fighter handbook was obtained by independent military research group Combating Terrorism Center (CTC), and published on Scribd by Yahoo.

Cyberwar: Anonymous already publish and update a list of Twitter accounts they claim spread propaganda in support of ISIS, a list which has now increased to 5,500

In it, jihadis are told to add a virtual private network (VPN) to their mobile browsers, which allows you to mask your location and use a foreign IP address, making it look to outsiders like you are in another city or country.

To send images or messages to each other, they use FireChat, which allows phones within a 200-meter radius to connect without using the internet, and emails are sent using encrypted apps.

The details have emerged days after it was revealed ISIS has its own 24-hour 'jihadi hotline' for technical difficulties.

Counter-terrorism analysts say the helpdesk is manned by senior operatives around the clock to support fighters using encrypted communication in order to evade the authorities.