Around 2.3 million online security threats are being blocked every day at New Zealand schools - or 1,592 every minute.
Such threats are becoming more sophisticated, with "malicious attempts to exploit IT system vulnerabilities rising substantially", according to Network for Learning (N4L), which connects schools across Aotearoa to the internet.
The Crown company also blocks dangerous or distracting websites and fends off incoming threats for the 2,457 schools in its managed network. They were up 17 per cent in terms 3 and 4, according to its latest report looking at the second half of the 2020 school year.
Chief executive Larrie Moore said while the rise was partly due to students returning to school after lockdown, it also reflected a rise in threats worldwide.
That's been demonstrated this week by the biggest-ever ransomware attack, which hit thousands of organisations that use Kaseya management software, including nine New Zealand schools and more than 100 kindergartens.
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The hackers had found a vulnerability in the Kaseya management software which a small number of New Zealand schools use on top of N4L, Moore said.
N4L's blocking services are led by global cybersecurity companies which constantly update the company as threats are discovered. But the Kaseya ransomware was a "day zero", never-before-seen piece of malicious software.
"When it was launched globally we all became aware of it at the same time." Such software is used in addition to N4L and is not directly within its remit, but Moore said N4L had worked with the Ministry of Education to mitigate the issue by quickly taking at-risk servers offline.
N4L's report found there were 491 blocks of incoming threats every day for each school, on average, up 68 per cent since the first half of 2020. A malicious adware tool called id5-sync - which tracks browsing and causes annoying pop-ups - was partly to blame, and was blocked more than 17 million times.
Phishing attempts and Distributed Denial of Service (DDoS) attacks were both down compared to N4L's report for the first half of 2020.
N4L also performs safety blocks - in terms 3 and 4 it blocked access to more than 45 million "dangerous or distracting" websites every school day - up 80 per cent on the first half of the year.
About 5 per cent of those blocks were for harmful digital content such as graphic violence and pornography. There were 5.6 safety blocks each day for each secondary student compared to less than one for primary students.
One per cent of total blocks were for pornographic images - but Moore said parents shouldn't be too alarmed by those figures. Much of the porn would have been pop-up ads appearing behind other, relatively innocuous content - and the technology ensure the children never saw it.
But Moore confirmed students could still access harmful content like porn on their own devices if they' used their personal data rather than school wifi.
All state and state-integrated schools use N4L but have some freedom over which websites to allow - some may block Instagram or Facebook while others use it for classroom chat groups to discuss school work.
Just over 20 per cent of blocks were for gaming sites, particularly Minecraft, Twitch and Steam. Another 14 per cent were for instant messaging and social networking sites.
The most commonly blocked "unsafe" websites were anonymisers - such as VPNs (virtual private networks) that let tech-savvy kids get around safety filters.
Research from Netsafe has found almost 50 per cent of teenagers have been exposed to potentially harmful content online, with parents often unaware of what their kids are seeing.
"We are continuing to seek an uptick in incident reports related to harmful digital communication and objectionable content, so it's important that N4L works with schools to block content from young eyes," Netsafe chief executive Martin Cocker said.