Page Two

By Larry Seltzer  |  Posted 2004-06-14 Print this article Print

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?)

For insights on security coverage around the Web, check out Security Center Editor Larry Seltzers Weblog.
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. Check out eWEEK.coms Security Center at for security news, views and analysis.
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Larry Seltzer has been writing software for and English about computers ever since—,much to his own amazement—,he graduated from the University of Pennsylvania in 1983.

He was one of the authors of NPL and NPL-R, fourth-generation languages for microcomputers by the now-defunct DeskTop Software Corporation. (Larry is sad to find absolutely no hits on any of these +products on Google.) His work at Desktop Software included programming the UCSD p-System, a virtual machine-based operating system with portable binaries that pre-dated Java by more than 10 years.

For several years, he wrote corporate software for Mathematica Policy Research (they're still in business!) and Chase Econometrics (not so lucky) before being forcibly thrown into the consulting market. He bummed around the Philadelphia consulting and contract-programming scenes for a year or two before taking a job at NSTL (National Software Testing Labs) developing product tests and managing contract testing for the computer industry, governments and publication.

In 1991 Larry moved to Massachusetts to become Technical Director of PC Week Labs (now eWeek Labs). He moved within Ziff Davis to New York in 1994 to run testing at Windows Sources. In 1995, he became Technical Director for Internet product testing at PC Magazine and stayed there till 1998.

Since then, he has been writing for numerous other publications, including Fortune Small Business, Windows 2000 Magazine (now Windows and .NET Magazine), ZDNet and Sam Whitmore's Media Survey.

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