The New Zealand stock exchange (NZX) has come under another cyber attack, bringing all trading to a halt.

The NZX was attacked yesterday afternoon, cutting trading short by an hour.

It opened this morning and traded for about an hour before coming to a halt.

A spokesperson said it appeared it was being affected in a similar way to yesterday's overseas distributed denial of service attack.

The attack overwhelms online service with more traffic than the server or network can accommodate, which makes the website or service inoperable.

Cyber attack difficult to stop

A computer scientist says the type of cyber attack on the New Zealand stock exchange is difficult to stop entirely but it is possible to shore up defences.

Dr Rizwan Asghar from Auckland University's School of Computer Science says it appears to be an attack known as a Distributed Denial of Service (DDOS)

In such an attack, large volumes of internet traffic are directed at a target, overwhelming servers and networks.

Dr Asghar said the NZX cybersecurity systems are likely to mitigate DDOS attacks.

Republished by arrangement