Over 1.4 million computers in China were affected by viruses during the week-long Labour Day holiday.
According to statistics, 1,421,198 computers were affected during the holiday from May 1 to 7, about a third more than during the same period last year.
"Most of the computers were affected by Trojan viruses because more Internet users play online games or shop online during the holidays," Dai Guangjian, an anti-virus expert with a Chinese company said.
The Trojan viruses steal passwords of users' online gaming or banking services, Dai said. China has roughly 123 million Internet users, most of whom are young people.