Industry Alliance Touts Authentication in Fighting Spam

By Larry Seltzer  |  Posted 2004-06-22 Print this article Print

AOL, Earthlink, Microsoft and Yahoo publish a plan for making the Internet more hostile to unsolicited e-mail through authentication based on IP domains and content signing.

Bringing together work done over the past year by vendors and standards bodies, a consortium of some of the largest e-mail providers on the Internet published a proposal Tuesday to advance authentication of e-mail as a tool to fight spam. The ASTA (Anti-Spam Technical Alliance), which comprises AOL, Earthlink, Microsoft and Yahoo, issued the document, here in PDF form. It endorses in a general sense the two technical approaches being developed in the industry.

IP-based authentication validates that purported senders of e-mail are in fact legitimate senders for their domains. Spammers often utilize weaknesses in current Internet e-mail standards to make mail appear to come from a different domain than that of the actual sender.
Both Microsoft and independent researchers have worked on systems using this approach and have developed a consolidated standard, called Sender ID, based on SPF (Sender Policy Framework) and Microsofts own Caller ID. Microsoft says this proposal will be submitted to the IETF within the next several weeks.

Authentication based on content signing, which uses cryptographic techniques and digital signatures, also ensures that the message is sent by legitimate senders from the domain of the purported sender. Yahoo has developed a specification for content signing of e-mail called Domain Keys and submitted it to the IETF in May.

The ASTA document also endorses certain best practices for actors in the e-mail industry. Among the recommendations to ISPs are to limit rates on e-mail by users and otherwise limit the use of port 25, the Internet port for e-mail sending; to close all open relays, which are e-mail servers open for all to use; and to detect and shut down zombied client computers, which are computers taken over by Trojan horses and worms and used to send spam.

Rate limiting could be a practical way to deter spammers, Larry Seltzer writes. Click here to read more. The alliance recommends that legitimate bulk e-mail senders comply with the law by not using forged e-mail headers, harvesting e-mail addresses through SMTP or Web pages without user consent or using misleading subject lines. It also urges that users install and make use of anti-spam, anti-virus and other security software.

All four members of the alliance plan to experiment with both authentication approaches, and all have implemented SPF to some extent. Microsoft and Earthlink have implemented Caller ID as well. None would commit to a time for implementing Domain Keys or another content signing specification, but Microsoft hopes to make recommendations on it by the end of the year based on ongoing testing.

In a conference call, alliance members emphasized that authentication itself is not an anti-spam technique, but that it is a tool to be used by filtering, reputation and accreditation systems to block spam and identify legitimate e-mail to let through.

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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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