If your plan was to remain anonymous <i>on FB</i>, it would. But that&#x27;s not what their .onion service is for.<p>The ingenuiety of the hidden service is that FB basically inverted Tor&#x27;s idea. Tor is really good at bypassing restrictive net filters, while at the same time it hides your browsing destination. So in effect FB turned a Tor address into their own highly resilient web proxy. Where a proxy normally provides a guarded way out of a network, the hidden service provides an otherwise untraceable way in.<p>Now, technically it is ~possible to identify FB-Tor traffic from regular Tor traffic. At least in some sense. Because the address is inside the .onion network, there are only half as many routing hops between the client and the server. So if you, as a well funded governmental adversary, first identify nearly all Tor traffic, you can then see which clients receive their responses notably faster than the rest.<p>These faster roundtrips are very likely using hidden services. If you then drill down even further, I am sure you should be able to identify a reasonably large fraction of your own subjects who are clearly accessing FB and thus stepping around the nationally imposed censure.<p>For the record, Alec didn&#x27;t consider the above traffic analysis attack particularly feasible. And we both agreed that the straightforward solution is to get a lot more traffic for hidden services in general. Once FB is not the sole huge site with a hidden service, their traffic cannot stand out.