Prime Minister John Key last night confirmed that an attempt to hack into a supercomputer at the National Institute of Water and Atmospheric Research (Niwa), was from an IP address in China.
But he cautioned against assuming it was part of the state-sponsored hacking from China that the United States has decided to publicly target.
He said the IP address in the case of Niwa, a Crown Research Institute, was from China, "although that doesn't mean at all that it is from a Chinese entity".
"They often masquerade behind a particular IP address but that doesn't mean that is the ultimate source of the attack," he said at his post-cabinet press conference.
Attempts to hack into the computer, dubbed FitzRoy, were unsuccessful, Niwa said yesterday.
After the unauthorised access was detected overnight on Thursday, the computer was shut down but was back online on Saturday night, a spokeswoman said.
The National Cyber Security Centre, part of the Government Communications Security Bureau, had been kept informed throughout.
The computer was used to run scientific models and services and no sensitive personal or client information was stored on it.
The United States last week charged five named Chinese military officers with hacking and stealing trade secrets.
Mr Key said cyber attacks were increasing with 134 in 2012 and 219 last year.
About 70 per cent were attacks on private sector entities and 30 per cent on public sector systems.
"These are quite sophisticated attacks on our both government and private sector systems."
The GCSB reform legislation last year allowed the bureau to work with private sector companies to try to protect them.
Mr Key would not hazard a guess about the motive for hacking into the Niwa computer.
But security specialist Paul Buchanan suggested in the National Business Review the hackers could be interested in the location of weather buoys or accessing links to weather satellites that could also have non-weather-related purposes.