BEIJING - When you are checking e-mails while enjoying a cup of coffee in a cafe or diner, there's an outside chance someone sitting nearby is considering a raid on your bank account.

Those who use Wi-Fi facilities of public places such as coffee shops and libraries are being warned to take more care with their personal details when using their computer online.

"It is very easy for a hacker to create a Wi-Fi network in public places, and anyone that gets connected with the hacker's network risks having their information stolen," said a researcher in Internet security surnamed Zhou at an institute affiliated with the Chinese Academy of Sciences. The hacker can create a network with a computer and a wireless relay and give a name similar to the one provided by the coffee shop or business providing the Wi-Fi.

Some customers may then access this decoy network, as it usually does not require a password, and end up having their personal details and password stolen, Zhou warned.

"Even if a customer gets connected to the Wi-Fi network provided by the shop, he still may get his computer hacked as Wi-Fi is not as secure as cable network," he said.

A man surnamed Zhao, who said he often went to a branch of a well-known coffee shop chain, said he had stopped going online there.

"I seldom use Wi-Fi in public places as nowadays there are too many hackers and loopholes in the Internet," he said. "And the possibility that anyone can create a Wi-Fi network (in the coffee shop) just adds another reason for not using the Internet there."

However, others seem less concerned about the risks.

Noelle Herring, a Californian who is studying in China, said she always uses Wi-Fi through laptop or mobile phone in public places.

"What's the big deal?" she said. "The worst thing that could happen to me is that I lose my credit number and password to hackers. Even then I am not too worried, as I have insurance for my credit card."

Another woman, a sales manager surnamed Ding, said she would only use Wi-Fi in public places to check news and e-mail, and would check financial accounts at home.

"I think hackers have targets, and these targets are people in senior positions who have business secrets," she said.

Zhou, the Internet security expert, advised that although no network was completely safe, users should take security precautions, such as installing a firewall and anti-virus software.

When using Wi-Fi in public places, people should also check to make sure they log on to the right network, Zhou suggested.

Yu Guofu, a Beijing lawyer who specializes in Internet matters, said that hackers who set up fake wireless networks faced up to seven years in prison if caught.

Those who provide high-tech tools to find loopholes in normal networks will be also punished, said Yu, from Sheng Feng law firm.

"Customers should be more careful when using network services in public places, while those who provide the Wi-Fi, such as cafes and book bars, should also upgrade their services so that customers can easily distinguish the authorized network from the fake one."