The commission is probing the intelligence and law enforcement response leading up to the Bondi Beach terror attack on December 14 which claimed the lives of 15 innocent people.
In a first block of hearings, witnesses from the Jewish community gave evidence about their experiences of anti-Semitism.
Commissioner Virginia Bell opened Tuesday's hearing with a warning to those engaging in online harassment and intimidation of witnesses.
"The commission is keeping a close eye on these instances and recording these offensive social media posts," she said.
"Quite what this undiluted level of hatred and bigotry directed towards members of the Jewish community is thought to benefit by those who post these remarks is lost on me.
"The commission has as one of its principal objects understanding and assessing the lived experience of anti-Semitism by members of the Jewish community and it is being informed by conduct of this character."
In the lead-up to the attack, NSW Police were warned by Jewish security group, CSG, that a heightened atmosphere of anti-Semitism made a terror attack on the community likely.
NSW Police Assistant Commissioner Leanne McCusker, who commands the counter-terrorism squad, told the commission on Monday she accepted a threat assessment should have been conducted for all Hanukkah events.
One of the recommendations made by the commission in an interim report released in April was that Jewish community gatherings be subject to tighter security arrangements.
ASIO director-general Mike Burgess appeared as the first witness on Monday, telling the commission Jewish holy events were identified as attractive targets for terrorists months before the Bondi Beach massacre.
Mr Burgess said it was extremely hard to detect such attacks if people were not discussing plans with a broader circle, including at prayer groups.
"We aren't all-seeing or all-knowing and we don't aspire to be," he said.
NSW Premier Chris Minns acknowledged the Bondi attack was an intelligence failure but defended the record of law enforcement agencies in preventing similar attacks.
He also pushed back on concerns a lack of communication between state and federal counterterrorism authorities was creating cracks for bad actors.
"We've clearly had a giant law enforcement and intelligence failure in December ... we need to correct and make better," he told media on Tuesday.
"These are law enforcement agencies that work with sophisticated technology and have had success in the past.
"You often don't read about it because they've acted before someone's committed horrible terrorism."
Responding to a report by the Daily Telegraph that authorities were warned about one of the shooters via a national security hotline as early as 2007, Mr Minns said it looked like warnings were missed.
"That's a very concerning piece of evidence that presumably will be fully investigated by the royal commission and we want to get to the bottom of it," he said.
17°C