The attacks have affected the private company NZX which hosts the market, halting trading for up to several hours at a time.
Finance Minister Grant Robertson said Friday that ministers had asked the Government Communications Security Bureau intelligence agency to help stop the attacks.
“We as a government are treating this very seriously,” he said, adding that security concerns prevented him from saying much more.
Neither the NZX nor Robertson said if the attackers sought a ransom, as some have speculated.
The security bureau declined to comment. NZX did not immediately respond to requests for comment.