Hacker group Anonymous have posted a video declaring war on jihad websites to avenge the attack on the satirical magazine Charlie Hebdo.
The group made the announcement via YouTube, saying it was a message for "al-Qaeda, the Islamic State and other terrorists".
The hacktivists also posted a blog Pastebin declaring it is their "duty to react" to the deaths of those killed on Thursday.
They say they will hunt down and close all social media accounts linked to any terrorist groups to avenge those killed.
The video shows a man dressed in the infamous Guy Fawkes mask worn by Anonymous saying the group will fight in memory of those who fought for freedom of expression.
"Against us you can do nothing. We are not physical, we are an idea, a cause, the voice of a free people," the video warns jihadists.
"We are Anonymous, we do not forgive, we will not forget, fear us, expect us murderer."
Anonymous is known for its high profile attacks on government, religious, and corporate websites.