Fighting advertising fraud still faces a big challenge in the domestic advertisement market, with the proportion of invalid traffic reaching 28.8 percent in the first half of 2018, according to statistics from AdMaster.

"The problem of invalid traffic has troubled both advertisers and the media," said Calvin Chan, CEO of AdMaster. "It has reduced media's traffic quality and influenced the results of effect measurement and audience analysis."

According to a white paper released from AdMaster, the proportion of invalid traffic in the first half of this year experienced a slight decrease of 0.8 percent and 1.6 percent, respectively compared to that of 2017 and 2016, reaching 28.8 percent.

Vertical media, which appeals to people in a single market or industry, is still the major target of advertisement fraud, with the proportion of invalid traffic reaching 40.8 percent, a 1.8 percent decrease compared with that of last year, the white paper said.

"Apart from the market status of supply and demand, the transparency of invalid traffic data may also account for the decrease," Calvin said. "Based on our data, advertisers tend to choose media with better qualities, thus reducing the invalid traffic."

According to the white paper, invalid traffic from March to May this year became even higher than that of previous year, reaching 22.4 percent, 20 percent and 21.9 percent, respectively, in March, April and May.

"January and June was the peak season for advertising in the first half of 2017," Chan explained. "As a result, advertisers this year choose to advertise in the less intense months, contributing to the increase in this period."

That said, according to Chan, the status of invalid traffic in the domestic market is becoming healthier, with more advertisers starting to include General Invalid Traffic, an important indicator of invalid traffic, in their assessment index.

"In the future, advertisers in the domestic market will put more efforts into reducing invalid traffic," he said. "We will cooperate with all sides and jointly build a healthy environment for the development of the digital advertisement market."

Fan Hang and Wang Jiaqi contributed to this story