From early on, I thought and said that the claim that the internet could not be controlled by state power was nonsense. If the USA had been able to get solid control, they might have been able to use it to encourage those rebel movements they approved of, while undermining the rest. But internets depend mostly on fast connections that governments can control when on their territory, or even passing through to a server under foreign control.
It’s also a remarkably useful way of spotting networks of dissidents. I’ve no hard information, obviously, but it is now generally agreed it has been done where the government is strong and determined. And I can speculate as to how:
Police get the communication records of some known dissidents, by tapping their communications or by using some cooperative burglar to break in and steal the data. Or by including a spy function in some attractive free download. They could then find:
Known dissident A communicates with B, C, D, E, F, G and H.
Known dissident K communicates with D, G, L, M, N, O and P.
Known dissident Q communicates with E, G, N, R, S, T, U and V.
So G is a prime suspect, in touch with all three known dissidents, who otherwise have little in common. D, E and N are also good candidates. The rest can be filed as mere friends of dissidents, but can be matched if they also communicate with some other known dissident.
Stage two would be to find out who G, D, E and N communicate with. If G and E communicate, that raises E’s profile. If E also communicated with H and P, that makes them worth investigating. There would also be new names, people not in touch with A, K or Q but in touch with at least two out of G, D, E and N.
(Real links and friendships would be much more numerous and complex, of course. But computers are wonderfully good at ‘data mining’, extracting interesting facts from a mass of dull facts in a way humans can not. Governments have their own experts, and can also hire people who’d do anything for money.)
Doing such a procedure a few dozen times would reveal the links and also eliminate the non-dissident friends of dissidents. Avoid bothering the sort of people who are sometimes turned from neutrals into foes by heavy-handed police methods, if classical methods are used.
Police can then arrest those who look like weak links. And reveal enough knowledge to falsely suggest an informer. They might tell K “we know that D, N and P are also dissidents, while L, M and O are just friends”. That might help make K a real informer and pass on extra details, and so on.
See also The Web is Always Insecure