China’s so-called “Great Firewall” keeps getting taller, deeper and more difficult to breach. This week state authorities acknowledged that China had recently upgraded the system of web filters that controls access to the World Wide Web in the country to more effectively block content.

Indeed, Chinese officials have confirmed to the Wall Street Journal that a speculated crackdown on VPN services is in fact occurring. To this point, VPN services had been one of the few tools Chinese citizens had to evade the firewall and access sites like Google and Facebook.

An anonymous Romanian VPN provider told the Journal that China’s upgraded firewall now appears to automatically find and block connections that are merely likely to be VPNs. Only known VPN connections had been blocked previously.

“Now it seems they are doing it automatically,” the source told the Journal. “You can apply some clever rules for the firewalls that will not trigger blocks.”

The new crackdowns come alongside new demands from the Chinese government that U.S. technology companies submit to intrusive inspections and turn over sensitive documents in order to do business in the country.

The lucrative potential of the Chinese market, however, ensures that at least some tech companies will comply with these demands. The Washington Post reports that the number of people online in China increased to roughly 650 million in 2014, with many on mobile devices. Hundreds of millions of Chinese citizens are active on social media as well, according to the Post.

In addition to the VPN outages, Instagram and Flickr also reportedly went dark this week as the new web controls went online.