Although I am not an expert, it appears that the “internet” as we know it works on the “honor system.” It’s clear that the Russins discarded the honor system and jammed most internet communications. Hence, the internet is pretty much non-secure (unless you have the military’s version at your fingertips).
Other than this current DDOS attack on Georgia I have only studied two other high profile attacks:

The hijacking of YouTube by Pakistan.

That was done by poisoning BGP routing tables. Or, simply put Pakistan fraudulently advertised that their routers had the shortest route to YouTube and then sent all the request into a black hole.

See: Youtube offline

http://www.datacenterknowledge.com/archives/2008/Feb/24/youtube_offline_pakistan_telecom_blamed.html

The Ron Paul case of Spamming which involved a clever Trojan program to turn thousands of computers in to email spammers. The same concept could be used for DDOS attack.

See: The Ron Paul bots and the Srizbi kernel mode Trojan

http://www.secureworks.com/research/threats/ronpaul/?threat=ronpaul