The chief information officer of the New Zealand stock exchange (NZX) has resigned and will leave the company at the end of 2020.

David Godfrey's resignation follows a series of distributed-denial-of-service attacks (DDoS) which caused multiple crashes of the trading website.

Such attacks disrupt service by saturating the network with significant volumes of internet traffic, and caused NZX to halt trading four days in a row.

NZX chief executive Mark Peterson said at the time he'd been advised by independent cyber specialists that the attacks are "among the largest, most well-resourced and sophisticated they have ever seen in New Zealand".

The Government Communications Security Bureau (GCSB) was directed to help the NZX with the attacks amid reports a crime syndicate was demanding Bitcoin payments.

• National security crisis apparatus gathered for NZX cyberattacks, GCSB targetted
• NZX boss tight lipped on cause of cyber attacks
• NZX website down again, trading unaffected

In a statement on Tuesday NZX announced Godfrey would step down after 11 years with the company. It is unclear if his resignation is related to the DDoS attacks.

Peterson said that Godfrey has been "an incredibly valuable and loyal member of the NZX team over the past decade".

"We are very grateful for the contribution David has made to the business. His attitude, commitment and support of everyone across the business  and through the wider capital markets community has been first-class."

An international search to appoint a successor is underway.