Dunedin internet users have better wi-fi security than Auckland and Wellington, making them harder for computer hackers to access.
NetSafe research showed Dunedin residents do the best job of using security measures to protect their wireless networks, compared with the other centres where more networks had little to no security.
NetSafe executive director Martin Cocker said too many homes of businesses were secured by weaker modem encryption codes WEP and WPA, which were easier for hackers to break into.
He advised people to secure their router with WPA2 and a long password.
The risk of unsecured wi-fi extends beyond freeloading, which costs many New Zealanders large sums of money, but also allows hackers to access all the devices on the network.