Silicon Valley firms moved to block the spread of the video of an Islamic State of Iraq and Syria (ISIS) militant beheading American journalist Steven Sotloff and see the execution as online propaganda.

The Sotloff video was uploaded on Tuesday on a website, but was quickly deleted when it was posted on YouTube. This decreased the number of posts linked to the video, according to an unnamed Silicon Valley insider.

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Some see the online execution as propaganda to propagate ISIS' beliefs and ideals. The footage of the same ISIS militant beheading James Foley, another American journalist, previously spread like wildfire via social networks, Nola detailed.

Social media sites such as Facebook, YouTube and Twitter do not allow images inspired by violence and hatred in their feeds. However, the general spread of such photos is difficult to control unless you know where to look online, Facebook safety advisory staff Stephen Balkam explained.

Balkam also said social media networks have become "better prepared" to push ISIS content away from the platforms after the Sotloff video came out.

In a statement, YouTube said it has policies against posting content that incite violence and they also take down videos that violate the rule once users flag it. Once the State Department identifies an account to be affiliated with terrorists, the video-sharing terminates it.

There are those, however, who are against Internet firms taking down content because of the inconsistencies in applying anti-violence policies. International freedom of expression advocate Jillian York said social media firms should remove content only when the law dictates that they should do it.

ISIS continues to use Twitter to recruit more members, York added.

Electronic Privacy Information Center (EPIC) director Marc Rotenberg suggests social networks should take down content related to ISIS and violence but not prevent users from discussing the issue. EPIC is a non-profit group in Washington that advocates freedom of expression and Internet privacy.

Most of the bigger content-sharing platforms will support national agencies' goal of removing content that may pose threats to national security or affect criminal probes, according to Dwayne Melancon, an executive at cyber security firm Tripwire.

TagsSteven Sotloff, online content, YouTube, ISIS