The New Zealand stock exchange (NZX) has come under another cyber attack, bringing all trading to a halt.
The attack shut down trading from about 11.20am. The NZX announced this afternoon it would reopen for trading at 3pm.
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.
AUT computer science Professor Dave Parry said these attacks were rare.
"It indicates whoever's doing the attacking is probably significantly skilled. These are quite sophisticated gangs and thinking along the lines of mafia type people is about right really, you're not really able to do this on a shoestring."
He expected the GCSB would work with Cert (Computer Emergency Response Team) to try to identify the attack's source.
"Unfortunately, the skills and software to do this are widely available and the disruption of Covid and people working from home all over the world potentially with lower security on their computers means that these attacks are easier than usual," Parry said.
Commerce Minister Kris Faafoi said he was advised it was likely a state actor was not behind the attack.
"I understand the ISP [internet service provider Spark] is working with NZX to try and make sure that its system is secure as possible. That's another example or opportunity to remind some of those larger entities that their systems are as secure as possible."
Investment adviser Brad Gordon of Hobson Wealth said there would be little or not impact on share prices.
"This [NZX] is only a mechanism for exchanging shares ... the share price actually reflects the company's performance ... it might impact the NZX share price in itself.
"It's certainly causing a lot of frustration for investors and I guess the biggest question is - given this is a repeat of what happened yesterday - how they get on top of it."
Cert's deputy director Declan Ingram said in a statement his team never confirms nor denies its involvement with any incident because the reports it gets are sensitive.
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.