The cyberwar began after a mid-air collision between a US spyplane and a Chinese fighter aircraft on 1 April. The Chinese plane crashed into the sea killing its pilot while the US plane and its crew of 24 was held by China. The crew was released 11 days later. As the US crew were still being held, US hackersbroke into hundreds of Chinese sites, leaving messages such as “We will hate China forever and we will hack its sites”. In response, the Honker Union announced it would launch its own electronic graffiti blitz. Tit-for-tat web defacements followed, causing damage to sites run in both countries.

At the time, the Honker Union called on Chinese software engineers to increase internet security on Chinese websites, which had been attacked by American hackers. Correspondents said companies from both countries scrambled to patch up security systems and to temporarily shut down web sites deemed a security risk. A statement by the Honker Union, carried by Chinese portal Chinabyte, says: “Any attacks from this point on have no connection to the Honker Union.” The Honker Union of China statement called for improving network security in China, and said that the sites that were violated were mostly small. “Because of this incident, network security in China will see great improvement. At least more people will become serious about building up network security,” the statement said.

Gao Yongan, an executive at the Beijing-based network security firm NSFocus, said many web sites would be vulnerable to hacker attacks until network administrators tightened up the security of their servers. Most hacker attacks, including web site defacements, are made through a chain of passive servers that act as springboards. Mr Yongan, who claims to be a reformed hacker, said: “The only way to solve this problem is to improve the global network safety level, and to make sure that no computers are available for attackers to use.”