The national internet service for schools says it is blocking millions of security threats each day.

The Network for Learning was blocking 1592 security threats a minute last year.

The network's report says internet use at the 2450 state and state integrated schools it covers increased 32 per cent in the second half of last year, compared to the first half when schools were shut for several weeks by the national pandemic lockdown.

It says streaming media sites such as YouTube and Netflix accounted for 24 per cent of the data consumed by the network in the last six months of 2020, and school internet users spent the most time on sites owned by Google, Apple and Microsoft.

The report says schools faced 17 per cent more cyber security threats in the second-half of last year and the network is blocking 2.3 million threats a day, more than half of them at secondary schools.

The network also blocked access to 45 million websites each day, including 2.2 million that contained harmful content such as pornography or violence.

The report says 25 per cent of the blocks involved file-sharing and storage websites, 20 per cent were gaming websites and 14 per cent were sites for social networking or instant messaging.

Network for Learning chief executive Larrie Moore told RNZ the organisation is blocking more security threats and more sites that schools had decided are distracting.

"By default we block 14 categories, then in addition to that we work with the schools and they advise us what other categories they would like to be blocked.

"So, for example, some schools might choose to block social media and other schools might choose to block social media and gaming and some schools might choose to leave both of those open, so it's very much schools decide," he says.

"Generally, globally, you're seeing an increase in the number of security threats and we're seeing that into New Zealand as well, so we're seeing that move up slightly and we're also seeing as more children connect devices to the internet we're seeing a number of blocks for categories go up as well. It's not a massive spike."

Moore says the network blocks thousands of ransomware attacks each day similar to the one that affected two New Zealand schools recently.

He says one of the affected schools is not on the Network for Learning and the other had vulnerable software on one of its servers.

He says the network ensures schools are well-protected from such attacks.

Moore says the network's data shows schools are using the internet to access sites that enabled students to collaborate with one another and to stream media such as videos.

"They're using the internet to support the delivery of education to the learners," he says.

He says school internet use is increasing as more children got access to a device to use in the classroom.

-RNZ.