We've seen some issues with AZ again today. On investigating it looks like more DDOS/abuse traffic from overseas. I've applied the same sort of block as last time we saw this, and things appear to have returned to normal..
The sharp drop is when the "attack" started, the jump is when it was blocked... the red line is blocked requests.
So this is still going on now. I've expanded the block to catch more of the dodgy traffic.