Facebook's last remaining tentpole product in China — WhatsApp — has reportedly been severely crippled by changes to China's internet filters, often known as the "Great Firewall."
New filters are specifically targeting WhatsApp functions, a source and several security experts told the New York Times. Many people are unable to send photos or videos, and some may not even able to send text, the app's main purpose.
The Times noted that based on the Chinese government's track record, a partial block could be the precursor to a full ban, though sometimes such disruptions are just temporary.
The government has tightened its grip on the internet in the past few weeks, most notably bringing new cybersecurity laws into effect. These in fact forced Apple to launch its first Chinese data center, since sensitive personal data must now be stored on local servers, and businesses must pass security reviews before they can transmit it elsewhere.
It's even expected that virtual private networks will be completely blocked in China by Feb. 2018, disrupting the one avenue Chinese residents had for circumventing the Great Firewall.
WhatsApp was already far less popular in China than a local messaging app, WeChat, but Facebook now has the barest of toeholds in the country, since both its namesake service and Instagram are banned.