The DHB said online scams were becoming more common, and more sophisticated. It blocked around 12,500 scam or malicious emails to its 6000 staff every day.
"This incident was a case of human – rather than system – error, and we remain confident in the robust security measures and protocols that protect our systems and data," said chief digital officer Tracy Voice.
"As a precaution, however, we have further enhanced our security measures and protocols. We will also strengthen our regular education for staff about these sorts of attacks and how to remain safe while using email and the internet."
Anyone who was unsure about an email received from a ccdhb.org.nz address should not respond and should contact the DHB on 04 385 5999. The DHB said it would never send an email request for personal or private information, account numbers or passwords.