The official, who spoke only on condition of anonymity because companies are grappling with increasing pressure to impose more censorship on the Web, would not say whether the developments came at the request of governments or ordinary users.
But after Foley's death, "platforms were better prepared for it this time around," the official said, adding that tech companies are trying to force out the Islamic State group "platform by platform."
Accounts on YouTube, Twitter and other sites were closed within hours of the video's release.
Even on Diaspora, a decentralized social network that does not exert centralized control over content, Islamic State militants are now often greeted with banners saying they are unwelcome. But they will find newly sophisticated ways to get a message out, said Jamie Bartlett of the Demos think tank in London.
Dwayne Melancon, chief technology officer at Tripwire, a Portland, Oregon-based cybersecurity firm, said videos have often already been "harvested" by users that download them and then repost the material on other sites.
"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," he said.
Facebook declined to comment on this instance.
Family Online Safety Institute CEO Stephen Balkam, who serves on Facebook's safety advisory board, said that when videos and photos are posted with the purpose of condemning violence, they are sometimes allowed to remain posted. But last year when beheading videos involving Mexican drug cartels were posted, it was obvious they were there to intimidate and they were pulled.
Balkam said many have gone online to condemn the Sotloff execution video and warn others not to look at it.
"It's been very interesting, with this second beheading, how very little of those images have been passed around," he said. "It's very difficult to find them unless you know of some darker places on the web."