Customers will get their missing money back after a scam attack against Hastings-based financial co-operative Unity credit union on Friday.
A post made on Unity's website warned they and some of their customers had been targeted by a "BIN attack" and a small number of cards were affected.
A BIN attack is where a fraudster takes the first six digits of a card - the Bank Identification Number (BIN) - and then uses a computer program to generate combinations of the rest of the card details until they find valid ones to make fraudulent transactions with.
A statement from Unity said the attack could have affected about 600 debit MasterCard cards out of their 55,000 members.
"The scammers, using technology that systematically generated card numbers and tested them for active accounts through a key merchant, were intercepted on Friday, 21 October and immediately blocked," the statement said.
"While the number of impacted members is small, Unity is working hard to make good on this BIN attack, and mitigate any further attempts to compromise their systems. Unity acknowledge this is disruptive to members and are doing everything possible to resolve the issue."
The statement said they were in the process of individually contacting each affected member and reversing any fraudulent charges.
Unity customer Janet, who declined to provide her last name for privacy reasons, said she was amazed by the quick service she got after she found money missing from her account on Saturday.
"I always check that account on Saturday morning, because we've got a rental and the money goes in during the week," she said.
She noticed $312 had been withdrawn from the account when did her regular check.
"I did a screenshot, and I thought I would just pop into the bank on Tuesday - I figured, 'I'm not going to get anybody over the weekend'."
She said her husband saw advice from Unity to use their support email on the company's webpage, so she decided to email them and got a reply back the same day.
"They said that the money would be back in my account [on Sunday] morning, that I could have an eftpos card on Tuesday if I wanted it, and my new debit card would be ready in eight days," Janet said.
"I just thought: 'This is amazing'."
Take your Radio, Podcasts and Music with you
