Pro-ISIS hackers have reportedly posted a video threatening to launch a global cyberattack on government, military, and corporate websites on Friday, Dec. 8 – with the U.S. as its first target.

“We will face you with a massive cyber war,” warns the group, known as the Electronic Ghosts of the Caliphate or Caliphate Cyber Ghosts, according to an International Business Times report. “Black days you will remember,” the video also proclaims.

Citing Raphael Gluck, lead analyst at JihadoScope, IBT reported that the the video first debuted on Monday and has been spread online via Twitter, Vimeo, Facebook and other platforms.

The Caliphate Cyber Ghosts are a subdivision of a larger ISIS cyberthreat group known as the United Cyber Caliphate (UCC), whom JihadoScope says recently resurfaced after a dormant period. UCC's hacking skills are not considered to be especially sophisticated, despite a history of taking over various social media accounts, the news report states.