Roland Dobbins has written to point out that the recent Russian cyber-attacks on Estonia are not the first launched by one state against another (he cites incidents during the Balkan confict, as well as China versus Japan).
Then he gives us an overview of DDoS attacks and mitigations:
DoS attacks are easy to trace as long as Service Providers (SPs) have the proper instrumentation and telemetry enabled on their routers – NetFlow is the most common way of doing this, along with various open-source and commercial tools (nfdump/ nfsen, Panoptis, Arbor, Lancope, Narus, Q1).
Most DDoS attacks these days aren't spoofed, because a) there's no need, given the zillions of botted computers out there available for use as attack platforms and b) because many SPs have implemented antispoofing technologies such as uRPF, iACLs, etc.
However, antispoofing (BCP38/BCP84) isn't universally deployed, and so the ability to spoof combined with DNS servers which are misconfigured as open recursors means that attackers can launch very large (up to 25gb/sec that I know of) spoofed DDoS attacks, due to the amplification factor of the open DNS recursors.
There are various mitigation techniques employed such as destination-based (destroys the village in order to save it) and/or source-based remotely-triggered blackholing (S/RTBH), plan old iACLs, and dedicated DDoS mitigation appliances; there's a lot of information-sharing and coordinated mitigation which takes place in the SP community, as well.
But there isn't nearly enough of any of these things, especially in the developing world.