Free and Open Port 25 Use Is Doomed - ' Page Two ' (
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Even after SMTP authentication is in place Internetwide, ISPs still must be vigilant about mail abuse. Authentication wont end spam, it will just end spoofing. (Yes, there are arguments about this, but I think basically it will end that aspect of the spam problem.)
Spammers will likely increase their use of cheap domains to send authenticated e-mail. (Incidentally, theres an inevitable source of future controversy. Services like ZoneEdit will become essential to spammers who want to operate using cheap but legitimate ISP accounts in the west. Should they ask no questions?)
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Scott Petry, Postinis founder, has been speaking lately about the declining effectiveness of content scanning and the inevitable rise of IP-based scanning. In other words, its getting harder for automated scanners to tell by looking at the content what is spam and what isnt. Spammers are getting better at making their spam look, superficially, like normal mail. What you have to do is look at the mailing techniques and the network sources of the message. Blocking port 25 at the client end is a brute-force manifestation of this philosophy.
As the Washington Post article makes clear, Comcast is far from alone in this practice, and you should expect eventually that almost all ISPs will jump on the bandwagon. For a company like AOL its even easier, since their own mail services dont use port 25. Port 25 abuse is so rampant on the Internet that ISPs should probably go further.
Ideally I think I agree with George Webb, a group manager of Microsofts anti-spam unit. According to the Washington Post article, "[Webb] thinks port 25 should be blocked by default, and customers should be required to apply for an exception." If youve got legitimate reasons to run port 25 services independent of those provided by the ISP and you have nothing to hide, the ISP should know about them. If you have privacy concerns with this, welcome to the 21st century.
Security Center Editor Larry Seltzer has worked in and written about the computer industry since 1983.
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