BEIJING -- The credit card transaction network of China Unionpay continues to operate normally despite a hacker attack, according to a spokesman from China Unionpay.

The attack only affected the official website of China Unionpay, he assured customers.

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According to previous reports, hackers on Friday planted a backdoor virus program on the website of China Unionpay (www.chinaunionpay.com), the country's only national electronic payment network operator, raising the risk of customer information being illegally accessed.

The spokesman, who declined to be named, said the attack was only aimed at the official website of China Unionpay, and confidential customer information had not been leaked.

Engineers at Rising Corporation, a leading Chinese computer security company, said Friday that the program, Backdoor.BlackHole.2005.a, is capable of hijacking customers' computers when they visit the website.

The engineers said the backdoor program was designed to attack computers installed with video cameras, through which the hackers could easily obtain access to the owner's private information.

But the program the hackers used is a relatively old version that can be neutralized by anti-virus programs, the engineers said, adding that computer users should update and activate their anti-virus software.

China Unionpay has over 172 million customers in China.