Qihoo, China’s leading anti-virus software provider, had a successful IPO in New York Stock Exchange yesterday.  Its share prices rose to over US$30 by 2:00 pm on its first day of trading.  This is more than double of its offering price of US$14.5.

The Beijing-based company, founded in 2005 by former Yahoo China head Zhou Hongyi, jumped to public prominence last year when it took on Tencent, China’s largest Internet company, in a high-profile battle after their initially quite different business interests started to overlap.

Zhou, 40, is a product of Xian Jiaotong University where he studied systems engineering. in 1998, he founded his first venture, 3721, an online service that allows users to access Internet websites using the company’s or the product’s Chinese name. It was sold to Yahoo for $120 million in 2004 and Zhou became head of Yahoo China, but the relationship ended on a sour note and he quit in 2005.

After being an angel investor for a while and working for venture capital firm IDG Capital Partner, Zhou was ready for another startup and founded Qihoo 360 in May 2005. In two years, it became most popular online network security services in China.

Zhou is generally praised for his ability to build hugely popular Internet services, but the measures he takes can be dramatic. His aggressive nature also offends many players in the industry.