Port 25 is used for POP mail by default on most email servers. So there are these spammers who just look for IP addresses which have port 25 open, connect to it and spam it with email. In some cases, it works. It is a huge burden on server resources, and bandwidth. It is the most annoying thing about spam!
So if South Korea does it (and they’re fairly Microsoft friendly there), will other countries in Asia follow suite? China might have it’s own plans for stopping spam.. since a lot of it comes from China itself.
It is a short term solution in my opinion. They will just connect to the new proposed port of 587 instead. But it will take time, and they have the advantage.. and it is legislation…
Zombie Storage has the lowdown:
Do these government agencies actually think blocking port 25 will reduce spam? Most of the issues stem from open relays (yes, I’ve noticed several on my IP block) or insecure servers. Botnets are a problem but using another port doesn’t fix that. From what I can tell they are also recommending people break port 587 by accepting both SMTPS and SMTP connections. Further they recommend 465 for SMTPS just to break the spec more.
The Korean government has long had a system of deep packet inspection so the technical implementation of a nationwide firewall over a port isn’t new or unprecedented. The steps may prevent some spam but really, I doubt it will amount to anything substantial. They can’t block all email and the system would probably fall over with IP forging techniques.
Update: I’ve asked a few people and it seems to be a joint initiative by the two departments and not actually a law. Although it does have penalties and apparently you get emailed warnings the first few times.
Original: http://zombie-storage.com/?p=95
Korean website: http://www.block25.or.kr/