It's an old one but it seems to be a good one for scammers. They pretend to be from brands such as Microsoft or Spark needing to fix your computer remotely, and it's on the rise again.
A victim is selected at random, such as Auckland teacher Shannon Nelson.
"Someone saying they are from Microsoft, saying there's a virus on my computer," says Ms Nelson.
Targets are directed to genuine files on their computer and told they're dangerous. The caller needs remote access to their computer to help, using programmes like Team Viewer, which is free to download. Once in, the scammers have complete control of your computer.
One Auckland businessman says scammers stole $5000 from his bank account within minutes of him giving access. All his personal details were also compromised.
But NetSafe says the scammers are professional cyber criminals and can be very convincing.
It took 162 calls last month from people who had been targeted, up from five in July – a total of $27,000 stolen or scammed. It's expecting September to be worse.
"I think New Zealand's phonebook comes up on the list and we get attacked every now and again, but also the upgrade to Windows 10 is confusing to some consumers and opens the doors to scammers," says NetSafe CEO Martin Cocker.
Microsoft New Zealand has been fielding hundreds of complaints. It says it never calls people to fix a problem.
"Get off the call," says Microsoft New Zealand marketing and operations director Frazer Scott. "If people have access to your computer, disconnect it from the internet."
Ms Nelson didn't get caught out, but she understands how others can.
"There was a barrage where they just kept ringing and I would pick up, hang up, pick up, hang up."
It's not just Microsoft; scammers are posing as callers from Spark, even government departments. The advice is to not even talk to the scammers, and just keep hanging up.