The video Tuesday showing the beheading of American journalist Steven Sotloff was first uploaded onto a different website and quickly deleted when copied onto YouTube, slowing the spread of posts linking to it, said a Silicon Valley insider, speaking on condition of anonymity because of the sensitivity of the topic.
Facebook, Twitter, YouTube and others all have policies banning terms of service regarding images of gratuitous violence or that incite hatred. But grisly images, once viral, are hard to restrain.
''It's been very interesting, with this second beheading, how very little of those images have been passed around,'' said Family Online Safety Institute CEO Stephen Balkam, who serves on Facebook's safety advisory board. ''It's very difficult to find them unless you know of some darker places on the web.''
When Tuesday's beheading video of Sotloff was launched so soon after Foley's death, ''platforms were better prepared for it this time around,'' the Silicon Valley insider said. Social media firms are trying to force out the Islamic State group ''platform by platform,'' the tech official said.
The major social networks declined to speak with The Associated Press directly about the beheading videos. But YouTube in a statement said it has ''clear policies prohibiting content intended to incite violence, and we remove videos violating these policies when flagged by our users.''
YouTube also terminates accounts registered by members of State Department-designated Foreign Terrorist Organizations and used in an official capacity to further their interests.
One advocate of free speech on the Internet said she's troubled by the idea of Internet companies removing content.
Jillian York, who directs international freedom of expression initiatives at the nonprofit Electronic Frontier Foundation, said corporations like Twitter and Facebook should never remove content unless required to do so by law.
''The problem is that their rules are applied unevenly,'' she said, noting that she has heard from numerous people who had their Twitter accounts banned after they shared the Foley video even though newspapers and the Israeli prime minister did the same without repercussion. Meanwhile, she said, the Islamic State continues to use the platform to recruit.
''Ultimately, though, giving corporations the power to censor sets a dangerous precedent,'' York said. ''And we've seen this power abused time and time again.''
Marc Rotenberg, director of the Electronic Privacy Information Center, a Washington-based nonprofit focused on Internet privacy and freedom of expression, said one strategy that is gaining support ''is to remove the underlying video but not to limit the discussion of the topic.''
Dwayne Melancon, chief technology officer at Tripwire, a Portland, Oregon-based cybersecurity firm, said most of the mainstream sharing sites will cooperate with national agencies to remove content deemed dangerous to national security or endangering an active criminal investigation.
''Even in these situations, videos have often already been harvested by users that download them and then repost the material on other sites,'' he said. ''This is the proverbial `the cat is out of the bag' problem we see all the time on the Internet. While you may be able to deal with the original sources of content, you're almost always dealing with multiple sources, many of whom will not listen to any request to `scrub' the video from their sites.''
Social media sites police their content around the clock to take down content that users flag. In the past, this has included images considered online bullying and pages or feeds from people who died or became incapacitated. In recent years, social media sites have repeatedly blocked extremely graphic videos of murders by Mexican drug cartels.