Half of the infected machines have suffered data loss, unbootable systems or difficulty in browsing the Web, the National Computer Virus Emergency Response Center said in its latest survey.

"Only 16 percent of computer users we sampled this year reported they were free from any virus attack, while last year, nearly one in three users said they suffered no computer infections," said Zhang Jian, chief engineer of the State-funded institution in Tianjin.

Along with the Ministry of Public Security and major anti-virus software suppliers, Zhang's center conducted the one-and-half month nationwide survey, which reported that computer viruses are the major threat to network security, as more people are using the Internet.

Unlike last year, when the main source of computer viruses came from compact and floppy disks, e-mails and online file swapping, the Internet has increasingly become the primary channel for the spreading of infections, Zhang said.

He said the first defence to fend off a virus is to enhance computer users' safety awareness and equip them with the necessary expertise to prevent and eradicate computer infections.

In another development, Win32/Bugbear, a fast-replicating worm that has wreaked havoc on millions of computers worldwide over the past 12 days, seems not to have infected many systems in China.

"Thanks to precautious measures, we haven't received a large number of reports from affected users," said Zhang Shuangqiao, vice-director of the Tianjin center.

Known as a mass-mailing worm because it spreads itself through computer users' e-mail programs, Bugbear was first identified by a security team in Sydney on October 1, according to security software maker Symantec.

Tian Yakui, an expert with the Beijing Rising Computer Technology Co, a leading anti-virus software vendor, said major computer anti-virus programs in China have already been updated to detect and kill the Bugbear worm.

(China Daily October 10, 2002)