Old and cheap modems are now being blamed for Spark’s broadband troubles.
Customers reported slow speeds and dropped connections over the weekend.
Spark now believes cyber criminals have gained access to a number of customer’s modems, and disrupted the network that way.
It has disconnected the affected modems, and contacting customers to discuss solutions.
Meanwhile, denial of service attacks which hobbled Spark’s internet over the weekend are extremely unlikely, according to an industry body.
Internet New Zealand’s work programme director Andrew Cushen says people arriving at work for the first time since Friday should run a virus scan on their computers.
But he doesn’t believe Spark will be a long-term target.
“These attacks are unfortunately quite common on the internet and they are used quite commonly overseas.
“We don’t see them often here in New Zealand, because denial of service attacks usually go after higher profile targets.”