The extremists of the Islamic State group have turned their social media into a theatre of horror, broadcasting a stomach-turning stream of battles, bombings and beheadings to a global audience.
The strategy is aimed at terrorising opponents at home and winning recruits abroad. But there are increasing signs of pushback - both from companies swiftly censoring objectionable content and users determined not to let it go viral.
Public disgust with the group's callous propaganda tactics was evident following the group's posting of the beheading video of American journalist James Foley - chilling footage that spread rapidly when it appeared online late on Tuesday.
The slickly edited video begins with scenes of Barack Obama explaining his decision to order airstrikes in Iraq, before switching to Foley in an orange jumpsuit kneeling in the desert, a black-clad Islamic State fighter by his side.
The fighter who beheads Foley is then seen holding another US journalist, Steven Sotloff, threatening to kill him next. "The life of this American citizen, Obama, depends on your next decision," he says.
By Wednesday, many social media users were urging each other not to post the video as a form of protest.
Phillip Smyth, a University of Maryland researcher who tracks the social media activity of jihadists, has noted a modest but noteworthy rise in the speed with which rogue accounts are being removed from Twitter and terror-supporting pages are being pulled from Facebook.
"It's happening," he said. "I can tell you first-hand because I look at this stuff every day."
The Islamic State group, an Al Qaida offshoot, has been a determined user of social media, broadcasting high-definition video of horrific forms of punishment including crucifixions, beheadings, stonings and mass slaughter.
A chilling, 61-minute video posted online in June, shows Islamic State militants knocking on the door of a Sunni police major in the dead of night in Iraq. When he answers, they blindfold and cuff him before they slice off his head with a knife in his own bedroom.
The fear created by such footage was seen as one factor behind the stunning collapse of Iraqi security forces when Islamic State fighters overran the cities of Mosul and Tikrit in June.
Faysal Itani, a resident fellow at the Atlantic Council, said the militants' slick production techniques are partly due to the foreigners who have joined their cause.
"They're the Twitter generation," he said. "They're good at it."
The Islamic State's adept use of the internet is in many ways an extension of Al Qaida's technological evolution, illustrating how much the group has changed since the Sept. 11, 2001, attacks and why it has flourished despite America's decade-long quest to crush it.
Unlike its Afghan Taliban allies, who banned television when they were in power, Al Qaida has never rejected modern technology. The group and its affiliates have exploited the Internet to rally and connect supporters, and are quick to adopt new technology.
Twitter Inc. says it's trying to keep the group's most gruesome videos off its platform, an issue that gained new urgency following the release of the Foley beheading footage.
In a tweet, CEO Dick Costolo said his company was "actively suspending accounts as we discover them related to this graphic imagery."
Smyth and others who track such activity reported a steep drop-off in jihadi posts after that. The number of images from Islamic State militants "dropped dramatically," researcher JM Berger said in a tweet, while Smyth said some 50-odd accounts associated with the group had been suspended.
Video-sharing sites saw a similar vanishing act.
On YouTube, which is owned by Google Inc., the images were posted for some time on Tuesday before being removed. By Wednesday, searches on YouTube mainly turned up links to news reports of Foley's slaying, or to reedited videos that removed footage of the beheading.
In a statement, YouTube said its policies "prohibit content like gratuitous violence," and it removes videos in violation when flagged by users.
Facebook said it began removing links to the Foley beheading on Tuesday, a process that continued Wednesday as users reported the clips. The Menlo Park, California, company said it was still allowing people to post snippets of the clip in the context of a discussion about the incident.
Even before Silicon Valley moved to quash the images, some users - many of them journalists - called on their colleagues to help prevent them from going viral. Organizing themselves under the hashtag "ISISmediablackout" they shared photos of Foley at work, copies of his articles and videos of his speeches.
For a brief period, a section of the social media world - generally full of look-at-me, look-at-this messages - was reduced to one stark request: "Look away."
For journalists and researchers alike, the censorship, even if self-imposed, raised some awkward questions.
James Lewis, a senior fellow at the Washington-based Centre for Strategic and International Studies and director of its strategic technologies program, said companies acted responsibly in removing the footage fast.
"Taking this stuff down off the social networks is important," he said. "You shouldn't suppress the facts, but you can suppress the image. That's just pornography."
Still, others noted that while urging a boycott of the video may help give people a sense of solidarity against a deplorable act, it also risks attracting more viewers out of curiosity.
"This kind of thing can put you in a bind because by stating that you don't want it publicized, you are publicizing it," said Steve Jones, a University of Illinois at Chicago professor who studies the cultural impact of social networks. "When you say to someone, 'Don't look at this,' the usual reaction is: 'Oh, why not? Maybe I should see this for myself.'"
Smyth said that there was a tension between allowing or encouraging everyone to see the brutality of militant groups like the Islamic State and stifling their propaganda.
"Part of me would have said: 'Allow this to spread because we need to know what kind of enemy we're dealing with.' But as time goes on, I've seen how manipulative they can be," he said.
He said he's seen jihadists boast on forums about how many thousands of "likes" this or that video has received on Facebook.
"They want people to spread these images, to spread their narrative one way or another."