China started censoring certain parts of WhatsApp, according to <a href="http://www.bbc.com/news/business-40651951" target="_blank" rel="noopener noreferrer">reports</a>. Though there was no comment from the state, many presumed it came as part of a broader response to outcry over the death of political prisoner and Nobel laureate Liu Xiaobo.
Using the so-called Great Firewall of China, or another part of its vast censorship apparatus, China managed to stop users sending WhatsApp video messages and other multimedia. But, given Facebook&#8217;s added security, including its <a href="https://www.forbes.com/sites/amitchowdhry/2016/04/06/whatsapp-brings-full-end-to-end-encryption-for-all-one-billion-users/" target="_blank" rel="noopener noreferrer">end-to-end encryption</a> of WhatsApp messages, how could the Chinese censor images and video while allowing the app to otherwise function as normal?
Turns out, it&#8217;s very simple, according to computer science student and security researcher Frieder Steinmetz. He put together a video showing the possible method China is using, just on a massive scale. It simply redirects a phone&#8217;s access to the media files server used by WhatsApp, causing video and photo downloads to fail.
<iframe loading="lazy" title="How to block WhatsApp media file transmission" width="500" height="281" src="https://www.youtube.com/embed/kcdJL2FbJ6g?feature=oembed" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>
He redirected connections trying to reach &#8220;mmg.whatsapp.net&#8221; and &#8220;mms.whatsapp.net&#8221; &#8211; the servers for downloading multimedia content &#8211; to the IP address 10.0.0.1. This was done with his own firewall. Afterwards, he removes the redirection via the web interface of his firewall. That&#8217;s when the images can again be downloaded.
Obviously, this is a small-scale experiment. But it&#8217;s likely China could simply expand it using their control over the country&#8217;s internet. &#8220;I don&#8217;t know the first thing about China&#8217;s censorship infrastructure but I imagine it is pretty easy to accomplish,&#8221; Steinmetz added.
Could WhatsApp do more to fight such censorship? Possibly. WhatsApp&#8217;s encryption is based on that of another popular messaging app, Signal. The creators of that tool have a neat trick for preventing forms of censorship. A source familiar with the app&#8217;s workings said Signal chooses to host services on Google servers alongside a lot of others. No one can see which service is being used by a particular user as the connection is encrypted.
That means that if a country wanted to sensor a unique service, like Signal videos, then they&#8217;d have to block the whole Google server, knocking out all those others running on the same machine. Even for China that&#8217;d be a risky move, causing all kinds of international outrage, beyond that already felt over its latest censorship broadside.
WhatsApp declined to comment for this article. &#8211; Written by <a href="https://www.forbes.com/sites/thomasbrewster/" target="_blank" rel="noopener noreferrer">Thomas Fox-Brewster</a>, FORBES STAFF

Tag: encryption

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Why It’s Really Easy For Anyone To Censor WhatsApp