Spam can originate from almost anywhere that has an internet connection. All that it takes once the spam message has been created is a simple upload to an ISP. I think it would be pretty hard to track the country or region that ALL spam originated from.
Like Wintereise said, these areas where the majority of affordable ISPs are located.
Most spam is not "from" the USA. The server are -- cheap VPS, mostly. The actual spam origin is mostly China, India, Pakistan, Russia and Ukraine. And it's heavily weighted towards China (50%+), followed by India. Unqualified stats like this are completely stupid. Very little spam originates in North America (USA, Canada, Mexico).
Yeah I just had to axe 3 dedicated server orders I got because they were from them. It stinks but it's gotten to the point where I have almost have to do background checks on every dedicated/vps customer.
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