Anatomy of a Cyber Attack

On April 27 a cyber attack was launched against Estonia that lasted approximately two weeks. The attack targeted government, banks, and newspapers. Wired has up an excellent, though long, article about what went on and how Estonia defended itself. With the heavy reliance on internet for global commerce and communication, we need to figure out how to both defend from such an attack as well as what that means in our current alliances. Does a cyber attack on one of our allies mean we need to go to war electronically? What about with traditional military?