Jihadists are in the cross-hairs of US social networks who are battling to enforce policies banning gruesome videos showing beheadings or hateful scenes such as flaunting hostages.
The Islamic State group's success at disseminating propaganda on social networks such as Twitter or YouTube has in turn given rise to online communities dedicated to vigilantly reporting posts that appear to violate rules laid out in terms-of-service.
"We review all reported content against our rules, which prohibit unlawful use and violent threats," Twitter said in response to an AFP inquiry.
Twitter in August removed from its service photos and video of the beheading of US journalist James Foley that had been posted online by jihadists.
"We have been and are actively suspending accounts as we discover them related to this graphic imagery," Twitter chief executive Dick Costolo posted at the time.
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YouTube removes the videos from its site in accordance with its policy against "violent or gory content that's primarily intended to be shocking, sensational or disrespectful."
YouTube community guidelines available online include a "Don't cross the line" category that told people "not to post bad stuff."
"We encourage free speech and defend everyone's right to express unpopular points of view," the Google-owned global online video sharing platform said. "But we don't permit hate speech."
A video of British hostage John Cantlie was available Thursday at YouTube, but returning to the link a day later resulted in the display of a message saying it had been removed due to content violating terms of service.
The video could still be found at other spots at YouTube, highlighting the fact that unwanted content can be reposted at different accounts with the service chasing after it as flags get raised.
Flag icons on YouTube pages allow viewers to report videos, offering a checklist of reasons including violent, repulsive, hateful or abusive content.
YouTube makes exceptions for violence in posts by news outlets, in which reporters deliver stories about shocking events.
Social network Facebook flat-out bars extremist groups known for violent tactics from using the website, even if they promised to just post about harmless topics like favourite songs.
"We do not permit terrorist groups, such as ISIS, to use our site, and we do not allow any person or group to promote terrorism or share graphic content for sadistic purposes," Facebook said Friday.
California-based Facebook has a team of employees armed with automated search tools scour the social network for accounts associated with "terror groups".
