Hackers have stolen "significant sums of money'' from businesses on Auckland's North Shore in the past couple of months, police say.
The companies, who regularly order goods from China and have dealt with their suppliers for many years, received emails asking for the usual payment to be made into a different bank account.
When the businesses questioned the suppliers via email to query the change, they received confirmation the details were correct.
"In both cases, the email accounts belonging to the Chinese suppliers have been hacked,'' said Detective Chris Blake, from the North Shore police CIB.
"The confirmation email is also a fraudulent message that has again been sent by hackers who have accessed the Chinese email account.''
The crime only emerges several weeks later when the Chinese suppliers contact the New Zealand businesses to question why they haven't been paid.
Mr Blake said business owners should not be embarrassed about being over cautious when dealing with overseas suppliers.
"Even if you've dealt with the same company for many years, don't be afraid to phone and ring the person you always deal with if you get a request that slightly differs from your usual routine with that company,'' he said.
"We want to prevent any more Kiwi business owners from becoming victims of this type of crime, and so we'd urge people to phone their suppliers, rather than email.''