In the last two months, Cloudmark saw a major spam run from Romania using IPv6, an Internet specification that dramatically expands the number of IP addresses. But the problem is that IPv6 addresses are so plentiful that blocking an individual address has little effect on spam.
Conway said it's better for antispam products to throttle the number of messages that can be received from a block of IPv6 addresses. Cloudmark already flags 3.3 million of Romania's 14 million IPv4 addresses as having a reputation for spam, Conway said.
As it becomes more difficult to send spam from Romania, Conway said there are signs spammers may be using IP addresses in Belarus. "Spammers will follow the line of least resistance," he said.
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