Let's start with two.

First, the standards for smtp need to be improved and strengthened.

Second, ISP's need to take a more proactive network in protecting against malicious traffic; this includes incoming and outgoing. If the ISP's actred appropriatedly and stopped routing traffic from known cyber-gangs, much of the current malcious traffic on the web would disappear.

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I use Country IP Blocks as added security for my networks and servers.