Tech companies were better prepared to scrub the internet after a second grisly video showing the beheading of a US journalist by Islamic State militants was released, a Silicon Valley insider says.

Video showing the death of James Foley last month ricocheted through social networks in what many feared was a propaganda coup for the extremists.

• Execution video authentic: US

The tech official said a video released this week showing another beheading – of US journalist Steven Sotloff – was quickly deleted when uploaded to YouTube, slowing the spread of posts linking to it.

According to the terms of service for many social media companies, the posting of threats and gratuitously violent content is cause for suspension.

After Foley’s death, “platforms were better prepared for it this time around”, the official said, adding that tech companies were 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 decentralised social network that does not exert centralised control over content, Islamic State militants are now often greeted with banners saying they are unwelcome.

Chief technology officer Dwayne Melancon, of US-based cyber-security firm Tripwire, said videos have often already been “harvested” by users that download them and then re-post the material to other sites.

“This is the proverbial ‘the cat is out of the bag’ problem we see all the time on the internet,” he said.

“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.”

Family Online Safety Institute chief executive Stephen Balkam, who serves on Facebook’s safety advisory board, says that when videos and photos are posted with the purpose of condemning violence, they are sometimes allowed to remain posted.

But when beheading videos involving Mexican drug cartels were posted last year, it was obvious they were there to intimidate and they were pulled.

Balkam said many people online had condemned the Sotloff execution video and had warned 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.”