In the US and other developed countries shutting down the telephone network or the 'net would be a political and financial disaster for a government, though one imagines the idea has crossed more than one totalitarian mind. In LDCs, however, where the role of private and military channels assumes a larger role than here, cutting off popular communications may not have the same implications. So, what can they do?
One option might be the reprogramming of cell phones to take over the functions of the Internet. Many phones use the popular open-source Linux operating system and are sufficiently powerful and programmable to add web-serving and routing functions. Working as a router or server, a phone could become a node on the network, using its transmission power in lieu of wired servers. Because these new phone-based nodes would be entirely mobile and independent, they could function as a parallel Internet, entirely outside the control of ISPs and governments, without being easily located. Technically the process would be much like Voice Over IP telephony like Skype, in which peer-to-peer servers move the messages along instead of passing them through (government controllable). Ain't mobility grand?
The network functions would add demand to batteries, but this could be overcome with stockpiling and charging centers as well as by individuals; everyone would carry a spare. The alternate programming could reside on a removable memory chip that would plug into the same slot where one normally stores photos, etc. All this would be very, very hard to stop. The communications genie is out of the bottle.
Could terrorists do the same thing? Probably not. There are never very many of them, and they could never be densely enough concentrated to pass messages around an entire country.
External (international) communications could be achieved by having nodes within sympathetic embassies or ships in port, which often have satellite uplinks. This would all work very slowly compared to high-speed Internet service, but slow is better than dead.
We're not the techies to do this, but we'd bet they're out there. Civil rights, anyone?
* BANGKOK, Thailand (AP, reported by Mick Elmore on Sept 28) — As soldiers in Myanmar intensified their crackdown on pro-democracy protesters Friday, authorities also went after the Internet and mobile phones that have proven so vital and powerful in documenting the dramatic confrontations...The Internet has played a crucial role in the flow of information out of the reclusive Southeast Asian nation where few foreign journalists are permitted to operate and media freedom is severely restricted.