Scammers are using an ACC email address to try trick people into clicking a link that could compromise their email account.
The spam emails, sent this afternoon, appear to come from a legitimate @govt.nz or @co.nz email address and urge recipients to migrate to a new version of Microsoft Office.
ACC has issued an alert about the phishing emails.
"Under no circumstances should you click on the link ... If you get an email like this, do not click on any links or attachments."
It's not yet known how the emails were sent or how many people have received them.
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An email seen by the Herald appears to have been sent from a legitimate email address of an ACC employee.
It urges to click on a link to immediately migrate to a new Microsoft Office system so you can continue to access pay slips, the staff directory and email among other functions.
"All staffs/Outlook Users are expected to complete this process within 24 hours to avoid delay on mail delivery and to also enjoy the new outlook features.
"On behalf of IT Support. This is a group email account and it's been monitored 24/7, therefore, please do not ignore this notification, because it's very compulsory," the spam email said.
ACC said in a statement on its website that as soon as it was made aware of the emails, it took action to stop more being sent.
"We're confident no personal information was accessed, including contents of sent and received emails."
ACC said to contact CERT NZ to report a cyber security issue.