"I am reluctant to scan matrix barcodes recently, because you don't know how to identify whether they contain malicious codes or not until you read it with your phone," said Bao Lili, from Zhangjiakou city, who previously liked to scan codes for discounts such 5 yuan off the price of a movie ticket.

But the 29-year-old now refuses to scan codes because one of her colleagues lost about 300 yuan after accidentally installing malicious software.

"She didn't get her money back because she didn't know whom she could claim the loss from," she said.

Considering the ease with which codes can be made and their lack of supervision, Zhang Zhiyu warned users to be careful when scanning.

Li Yuxiao, a professor of social networks from the Beijing University of Posts and Telecommunications, agreed with him, adding that it is better to scan matrix codes from regular websites instead of from posters on the street or other sources.