In the order of most powerful to least powerful:

  1. Nation States
  2. Russian Criminal (and Soviet Republics)
  3. Hacktivists: Syrian Electronic Army, Anonymous, and LulzSec
  4. Sole Actor

According to Kevin Mandia these are the top 4 most powerful Cyber Warfare groups. Different nation states attack for different reasons.

Where Do I Focus?

What do you focus on? You focus on the things that you control! Primarily, you control your own environment, so fix that first. Secondarily, focussing on the outsourced managed providers, third parties, and business partners.