A pro-ISIS hacking group has threatened a massive cyber attack on governments and armies around the world starting with 'the cursed Unites States' tomorrow.

Electronic Ghosts of the Caliphate declared in an ominous video to its enemies: 'We are the hackers of ISIS. We will face you in a massive cyber war.'

The video features a distorted voice saying in Arabic: 'We will penetrate the websites of governments, military ministries, companies and sensitive global sites.'

It shows tomorrow's date as the voice says: 'The first goal is the cursed United States, the head of the snake. Black days you will remember.'

Asked if the threat was credible, one expert told MailOnline: 'It's impossible to say for certain because we never know what's next with ISIS.'

A pro-ISIS hacking group has threatened a massive cyber attack on governments and armies around the world starting with the US tomorrow

One screenshot from the video shows tomorrow's date with the caption: 'Black days you will remember'

The Electronic Ghosts group is one of four which joined forces in 2016 to create the United Cyber Caliphate which was dormant until 24 November.

Raphael Gluck of monitoring group JihadoScope told MailOnline: 'With the exception of hackers like the now-deceased Junaid Hussein, ISIS' level of hack has been very low.

'The United cyber caliphate claims to be hacking social media accounts but what it's really doing, if anything, is taking control of some very dormant accounts from 2012 or something like that. These accounts have older and shorter passwords so are easier to hack.'

Gluck said it's unusual for groups to name the date of their attack and suggested the video posted on Monday was an attempt to 'project a great threat.'

He added: 'The other week an anti ISIS group called a "hack ISIS" day for November 17. This turned out to be a bit over hyped but it might be the reason behind them naming a date.'

Electronic Ghosts of the Caliphate declared in an ominous video to its enemies: 'We are the hackers of ISIS. We will face you in a massive cyber war'

The group is threatening to penetrate websites including government and military

The increased cyber threat comes as ISIS collapses in Iraq and Syria.

Yesterday the chairman of the US Senate Homeland Security Committee said: 'This is the new caliphate - in cyberspace.'

US national security officials told senators that the collapse of Islamic State in Iraq and Syria has not diminished the group's ability to inspire attacks on Western targets via the internet.

Lora Shiao, acting director of intelligence at the National Counterterrorism Center, told a US Senate committee: 'Unfortunately, we don't see ISIS' loss of territory translating into a corresponding reduction in its inability to inspire attacks.'

'ISIS' capacity to reach sympathizers around the world through its robust social media capability is unprecedented and gives the group access to large numbers of homegrown violent extremists,' Shiao said.

The US-led coalition estimated on Tuesday that fewer than 3,000 ISIS fighters remain in Iraq and Syria, where they declared a caliphate in 2014.

The US-led coalition estimated on Tuesday that fewer than 3,000 ISIS fighters remain in Iraq and Syria

ISIS was driven out of Raqqa, the Syrian city it called its capital, in October, prompting President Donald Trump to say 'the end of the ISIS caliphate is in sight.'

Yet 'the elimination of the physical caliphate does not mark the end of ISIS or other global terrorist organizations,' said Mark Mitchell, acting assistant defense secretary for special operations/low-intensity conflict.

As ISIS loses territory it will become more reliant on virtual connections, he said, and continue to inspire 'stray dog' attacks by vulnerable people.

Senators questioned the security officials about US efforts to fight online recruitment of potential extremists.

They described an evolving threat including ISIS' ability to adapt its narrative after territorial losses to portray the struggle as a long-term process.

The internet is the primary tool for radicalization and no group has been more successful than ISIS in drawing people into its message.