The New Zealand stock exchange system and website was hit by a malicious offshore attack this afternoon.
NZX Limited, which is a Spark customer, experienced what's known as a distributed denial of service (DDOS) attack from offshore.
The attack works by overwhelming the online service with more traffic than the server or network can accommodate, with the goal to render the website or service inoperable.
The NZX decided to halt trading in its cash markets just before 4pm.
The attack was able to be mitigated and connectivity has been restored for NZX.