The New Zealand stock exchange (NZX) website has gone down again in what appears to be the latest disruption caused by cyber attackers.
The NZX website has been targeted by repeated distributed denial of service (DDoS) attacks over the last week, beginning last Tuesday.
Such attacks disrupt service by saturating the network with significant volumes of internet traffic, and have caused NZX to halt trading four days in a row.
The latest outage comes less than an hour after NZX revealed it had contingency arrangements in place with the Financial Markets Authority should its website go down again.
The arrangements, which come after NZX teamed up with cyber defence experts Akamai Technologies, are for the release of and access to market announcements that are intended to allow trading to continue.
NZX chief executive Mark Peterson said he'd been advised by independent cyber specialists that the recent attacks are "among the largest, most well-resourced and sophisticated they have ever seen in New Zealand".
On Friday, the Government Communications Security Bureau (GCSB) was directed to help the NZX with the attacks amid reports a crime syndicate was demanding Bitcoin payments.
In an appearance on The AM Show on Monday, Rush Digital founder Danu Abeysuriya told host Ryan Bridge the attackers can be difficult to track.
"Whoever's doing it has a lot of resources organised - so it could be a really cashed-up criminal gang, which is highly likely, or something more," he said.
"It's highly likely that it's a ransom-type attack."
Abeysuriya said technology company Garmin recently paid a ransom of about 10 million Euros following a cyber-attack.