Information technology experts say despite an increase in the number of reported cyber attacks against Government agencies and the private sector, the real figure is likely to be much higher.
A report on the issue was published on Thursday by the National Cyber Security Centre, part of the Government Communications Security Bureau. It showed there were 134 recorded threats in 2012, up from 90 in 2011.
GCSB director Ian Fletcher says the centre deals with at least three serious attacks each week, but officials know many more are never reported.
Scam and spam related incidents made up 31% of the reported activity last year.
Denial of service attacks, in which networks are shut down and held for ransom, and malware activity were the next biggest categories, at 16% and 14% respectively.
Domain Name Commission manager for security policy Barry Brailey said the recorded threats are likely to be just a fraction of the total cyber attacks.
He says most businesses and private sector organisations prefer to deal with cyber attacks in-house to avoid scaring customers.
Technology blogger Keith Ng last year identified serious security flaws in Work & Income's systems.
Recent attacks on Yahoo! Xtra show big corporations are flawed at protecting data entrusted to them, he said.