According to SITE Intel Group, which monitors jihadist social media, the Islamic State of Iraq (ISIL) and the Levant threatened to go through with a cyber-attack against the UK. ISIL made its threat in an online video, opening with images of combatants carrying long knives and ordering a group of Western hostages to march forward and kneel in the dirt.

This development comes weeks after the UK carried out a drone attack in Syria to kill an Islamic State fighter with a British background who was suspected of planning attacks on the UK. Prime Minister David Cameron told Parliament on 7 September that he did not seek approval from lawmakers as the strike was ordered in self-defence.

“We take cyber-threat very seriously,” the UK government said in an emailed comment. “We have taken action to defend our networks against increasingly sophisticated attacks.”

UK defence secretary, Michael Fallon, said on 8 September that the government was ready to order another drone strike on Islamic State militants if they were discovered to be plotting attacks against Britain.