Within hours of Saturday's deadly rampage at Westfield Bondi Junction, social media users uploaded distressing footage of the attack while others falsely claimed the carnage was a "false flag" event secretly orchestrated by shadowy figures.

"I'm concerned by social media at times like this ... where everyone is a publisher, it can create some real difficulties," Prime Minister Anthony Albanese told reporters in Canberra on Tuesday.

"And I just say to people: 'think before you press send because this can have a really disruptive impact on people'."

The eSafety commissioner called for people to think critically before commenting online and not to use social media as a tool for division.

"This includes refraining from inferring motive or intent behind these heinous crimes or pointing fingers towards any groups or individuals who might be responsible without formal verification from official sources, such as government or police," Julie Inman Grant said in a statement.

The knife attack was carried out by Joel Cauchi, 40, a Queenslander with long-term mental ill health, whose father described as "a very sick boy".

Six people died in the attack before Cauchi was shot dead by a police officer.

Jolanda Jetten, psychology professor at the University of Queensland, said conspiracy theories about disasters were attractive to some people "because they provide a simple explanation for complex causes".

"Mental health is not an easy one to understand nor why it leads to this type of violence," Prof Jetten told AAP.

"So the idea that there must be something more going on at Bondi overrules the notion that it could be a sole perpetrator with mental health issues."

Associate Professor Patrick Stokes, a philosophy expert at Melbourne's Deakin University, said some studies showed the number of conspiracy theories had remained relatively stable.

However, he said modern technology allowed misinformation to develop and spread far more quickly than before.

"We saw that on the weekend with the attack in Bondi. We saw that false attributions of blame immediately spread really quickly," Dr Stokes told AAP.

"As soon as there's any kind of mass casualty event, we immediately hear about it from a number of sources."

The Sydney stabbings are the latest in a long line of attacks and disasters wrongly labelled as false-flag events by conspiracy theorists, including the 2012 Sandy Hook school shooting in the US, the September 11, 2001, terrorist attacks, the 2017 Manchester Arena bombing, and the recent Baltimore bridge collapse.

Dr Stokes said people attracted to conspiracy theories often distrusted institutions such as governments and the media.

He said it could also be comforting for some to believe disastrous events were planned instead of random.

"Telling a story about who's behind it and which powerful actors are really doing this ... that's more comforting than the thought that a random person can inflict that kind of carnage."

"There's something perversely calming about conspiracy explanations in that they do actually give us back the possibility of control."

Australian Associated Press