The founder of 8chan has called for the website to be shut down after the El Paso shooter allegedly posted a racist manifesto to the forum before carrying out his attack.

Key points: The website is an online message board that is largely unmoderated and anonymous

The website is an online message board that is largely unmoderated and anonymous A racist manifesto believed to be linked to the El Paso massacre was posted on the site

A racist manifesto believed to be linked to the El Paso massacre was posted on the site Internet security firm Cloudflare has cut ties to 8chan over the shooting

A 2,300-word rant against Hispanic Americans was posted on 8chan just moments before a gunman killed at least 20 people at a Walmart store in El Paso, Texas, on Sunday.

US authorities believe the racist, anti-immigrant screed was the work of the alleged shooter, 21-year-old Patrick Wood Crusius.

The El Paso massacre is at least the third atrocity this year where a suspect is believed to have posted to 8chan in advance of an attack.

The gunman opened fire on a crowded Walmart in El Paso, Texas, after allegedly posting a racist rant on 8chan. ( ABC News: Niall Lenihan )

The founder of 8chan, Fredrick Brennan, who has since cut ties with the site, told PM's Sally Sara that he created a "monster".

"It really just seems like they think all these shootings are funny, like they really don't care … and it just seems like they're just going to keep allowing this to happen over and over," he said.

Mr Brennan launched the message board in 2013 as a space that welcomed all speech — no matter how extreme.

It has since become a host to some of the most vitriolic content online.

"People say, 'you have created kind of like a Frankenstein's monster, you were not really thinking about the effects this could have on society … and now it's come back to haunt you,'" he said.

"I can see the comparison … I feel like maybe I did create a monster. But their administration is making it much more monstrous than it has to be."

Mr Brennan said he thought the current administrators should do more to shut down hate speech.

"I'm not saying they could prevent these attacks from happening, but there are things they could do to show that it's not appropriate to post a manifesto from a shooting on that site," he told the ABC.

"They could shut down the boards that are known for being places where people celebrate mass shooters after a mass shooting occurs — that would be a good first step."

What is 8chan?

Mr Brennan founded the 8chan message board in 2013 to be largely unmoderated and for all posts to be anonymous.

He admits he started the site because he was an "angry teenager" who resented that he had a disability and must use a wheelchair.

The 25-year-old once wrote on a website that promotes white supremacy that people with disabilities should be offered incentives to not have children.

"But I wasn't for forced sterilisation or anything like that," he said.

8chan remained relatively unknown until 2014 when anti-feminist gamers were kicked off rival message board site, 4chan for harassing women.

The site was blacklisted in 2015 from Google search results due to the child porn content shared on certain boards.

Its "politically incorrect" board in particular has become an online meeting space for neo-Nazis, white nationalists and the alt-right.

Mr Brennan resigned from the site in 2016, and it has since been controlled by owner Jim Watkins and his son, Ron.

In March this year, the man accused of killing 51 people in the Christchurch mosque shootings, Brenton Tarrant, allegedly posted a manifesto to 8chan which expressed white supremacist views.

The following month, a racist rant was also posted to the site before a man shot up a California synagogue, killing one woman.

But 8chan is only the "tip of the iceberg" for online extremist websites, according to Dr Kristy Campion, a terrorism studies lecturer at Charles Sturt University.

"There are so many other places where they can essentially immerse themselves in the ideas and ideologies around right-wing extremism," Dr Campion told the ABC.

"There are platforms out there that are willing to have that sort of content on them, so shutting down 8chan will not shut down the exchange of ideas."

Network provider cuts off 8chan

Internet security firm Cloudflare, which helps to keep 8chan online, announced it would stop providing support for the website.

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Cloudflare initially refused to cut ties with 8chan, claiming that such a move would not make the internet safer or reduce hatred online.

However, the company's CEO said he has since had a change of heart.

"The rationale is simple: they have proven themselves to be lawless and that lawlessness has caused multiple tragic deaths," Cloudflare CEO Matthew Prince said in a statement.

"Even if 8chan may not have violated the letter of the law in refusing to moderate their hate-filled community, they have created an environment that revels in violating its spirit."

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Cloudflare protected 8chan from Distributed Denial of Service (DDoS) attacks, which are malicious attempts to disrupt normal traffic to a website.

The website has declined to comment on the El Paso shooter's alleged link to 8chan.

However, it informed followers on Twitter to expect delays once Cloudflare stopped protecting the site.

"There might be some downtime in the next 24-48 hours while we find a solution (that includes our email so timely compliance with law enforcement requests may be affected)," 8chan said.