Google has banned ads for virtual private network (VPN) products targeting Chinese users, ZDNet has learned today. The company cited "local legal restrictions" as the cause of the VPN ad ban.

"It is currently Google Ads policy to disallow promoting VPN services in China, due to local legal restrictions," Google said in an email today.

The email was received and shared with ZDNet by VPNMentor, a website offering advice, tips, and reviews of VPN products.

The company said Google prevented its employees from placing Google search ads for the Chinese version of its site.

When reached out for comment, a Google spokesperson told ZDNet the ban on VPN ads in China isn't a new development.

"This is not new," the spokesperson said. "We have long-standing policies prohibiting ads in our network for private servers, in countries where such servers are illegal. All advertisers have to comply with local law."

However, the company didn't answer our questions directly, if the ban was put in place on Google's own decision or after a request from Chinese officials.

The Chinese government has been on an all-out war against censorship-thwarting software, such as web proxies and VPN apps, for years.

The Chinese state recently tightened its grip on the local VPN landscape in January 2017, when it started requiring that all VPN providers active in China register for an authorization from the Chinese government.

Officials continued their VPN crackdown in July 2017, when the Chinese government forced Apple to remove all VPN apps from its App Store.

A full-out ban on all VPNs was imposed on March 31, 2018, although some apps continued to function after it.

Nonetheless, Chinese officials are now using the ban to go after users caught using VPNs. The first fine for using a VPN product was issued earlier this year to a Guangdong.

Despite banning consumers from using VPN apps, China remains one of the top sellers of VPN technologies. A November 2018 study found that almost 60 percent of the top free mobile VPN apps are run by companies with Chinese ownership or based in China.

Russia also banned VPN use in July 2017.

Article updated with comment from Google.

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