A chilling video depicting the apparent murder of a US journalist by jihadists is just the latest salvo in an online war being waged by extremists on social media sites.
Jihadist groups have long used their own media organizations to distribute messages and videos, but in recent years platforms like Twitter have given them an unprecedented, unfiltered ability to intimidate their opponents and recruit members.
Their use of forums like Twitter and video-sharing site YouTube has not gone unchallenged, with jihadist accounts frequently shut down, though many quickly reopen, in a cat-and-mouse chase between administrators and users.
The video that shows the brutal killing of James Foley by jihadists from the Islamic State group appeared on YouTube on Tuesday night. It featured hallmarks of jihadist videos reaching back at least a decade, but unlike images of gruesome killings during the height of the Iraq war, or the 2002 murder of journalist Daniel Pearl in Pakistan, it spread rapidly across the Internet.
YouTube quickly pulled the footage, but it was embedded elsewhere, and screenshots flashed across Twitter. Supporters and members of IS quickly spread the images and defended them, posting pictures of abuses by US troops at Iraq's Abu Ghraib prison and citing religious precedent for decapitation.
Foley had covered the war in Libya before heading to Syria, where he contributed to news site GlobalPost, Agence France-Presse and other media outlets. But online, jihadists accused him of being a spy, or claimed he deserved to die simply for being an American non-Muslim. He was dressed in orange clothes in the video, as jihadists online pointed out, in a reference to the jumpsuits worn by Muslim detainees at the US Guantanamo Bay facility.
Twitter users online made it clear Foley's death and the video were intended to spread fear.
"IS execution of the American journalist was a deliberate strategy, by showing brutality to the world puts the fear in IS enemies," tweeted one self-described "extremist" under the name Abu Bakr al-Janabi. "It's meant to evoke fear, terror and hatred," he added, writing in English.
"#AmessageToAmerica Islamic State will not leave any non-Muslim USA citizens alive in all Arab countries because (of US President Barack) Obama's airstrikes," added the KhilafaMedia Twitter account.
In recent years, Twitter and sites like the question-and-answer forum Ask.fm have become prime platforms for jihadists who would have once shunned such public exposure.