Warning: This story contains details some readers might find distressing.
Campaigners are calling for tighter restrictions on illegal sexual content online to stop children being accidentally exposed to internet pornography.
Pornography researcher Jo Robertson is calling for more action on filtering illegal content such as child sex abuse.
Michaela* and Jade* have children who have have stumbled across rape and child abuse material online.
For privacy, and due to the sensitivity of this topic, RNZ has agreed to keep both Michaela and Jade anonymous.
Michaela became suspicious of her oldest child's behaviour, so checked her three children's internet search history.
Her nine-year-old accessed porn while doing her homework, while her 10- and 11-year-old children were shown porn by friends, and also saw a violent sex scene from a movie on YouTube.
It took a huge toll on them, she said.
"I noticed all three of them had a lot lower moods. Two of them in particular got really depressed after discovering porn and then led to some unsafe behaviours in one of them and a lot of hiding, just not interacting with me in the same kind of open and carefree way that they used to," Michaela said.
She said her children suffered from nightmares and spent years in therapy to help them get out of a pattern of seeking pornographic content.
Jade, said her teenager was traumatised after accidentally seeing rape and bestiality material.
"Just distress, because obviously in those situations there's an innocent involved online and the welfare of that other person or being online."
Robertson, who is also a sex therapist, said New Zealand was falling behind other countries.
"Australia at the moment, they're really putting pressure on internet providers to create safer platforms and they're looking at creating consequences if internet providers don't actually perform in the way that they expect. We've got other countries trying to talk about age verification and filtering.
"What New Zealand is doing is an impoverished version."
Robertson wanted all internet service providers to put default safe search settings on modems for all new customers, which users could later opt out of.
Her Makes Sense campaign's petition calling for changes has so far received more than 2000 signatures.
The mothers said if filters on illegal sexual content were mandatory safe search settings were on modems, it would have saved their children a lot of torment.
"I think it would have delayed how soon they would have been exposed to stuff like that, so I think it would have protected them and shielded them from a lot of that shame and depression and stuff that they went through," Michaela said.
The Department of Internal Affairs (DIA) set up a voluntary Digital Child Exploitation Filtering System for internet service providers in 2009.
DIA deputy director of digital safety John-Paul Michael said more than 90 percent of New Zealand's ISPs were part of the system.
That included the three main telecommunications companies, Spark, One NZ and 2Degrees.
The department had the right to ask other websites not covered by the filter to remove any content classed as objectionable or unlawful under New Zealand law.
"The challenge that we have, by reaching out to some of those websites, is many of them are based outside of New Zealand and are not governed by our laws," Michael said.
That meant they might refuse to follow it a takedown notice issued by the department, he said. "Then it creates difficulties on how we can actually resolve that moving forward."
In a statement, Spark said it supported the government's efforts to block child sexual abuse material.
"We empathise with the desire to protect children from extreme and violent porn. However, we have always maintained that it is not appropriate for individual ISPs to determine what should be censored within our society.
"These policy decisions need to be made by the government in consultation with the people of New Zealand. This is how the DCEFS operates - government determines what content is blocked, and ISPs apply the filter."
While Spark's modems don't have a button for a safe search option, it provides all its broadband customers with free access to Net Shield which allows them to block pornography, illegal, abusive and graphic content online, the company said.
Internal Affairs Minister Barbara Edmonds said in a statement the government was reviewing how it regulated online platforms and other forms of media.
She acknowledged the government needed to lift the bar for safety when it came to protecting children and young people online.
*Names changed for privacy
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