Dont know if its an attack on my site but every time I send out my 100,000 email campaign there comes a time towards the end of the campaign that I get visited by a several amazon AWS servers at one time. I dont know if its a deliberate attack or if it has to do with me sending my emails using amazon. Here is a snapshot of the visited computers. I can see them coming because my chat widget alerts me of all my visits and I notice they are coming from Ashburn VA. When they do this it brings my CPU useage way up and I have to go into my sucuri firewall and block each ip.
See snapshot.
See snapshot.