MS Caller ID Plan Boosts SMTP Authentication

By Larry Seltzer  |  Posted 2004-02-24 Print this article Print

News Analysis: Bill Gates' Tuesday announcement of Caller ID at the RSA Conference was the biggest boost ever for SMTP authentication technology. Yahoo! also chimed in with some news on its similar Domain Keys proposal.

Microsoft Chairman Bill Gates on Tuesday announced a proposed open standard to deter e-mail spoofing, a k a caller ID for e-mail. Microsofts proposal pitched to the security experts at the RSA Conference falls right in line with the emerging industry consensus that changes must be made to the e-mail infrastructure in order to make serious progress in the battle against spam. The actual "Caller ID for E-Mail" specification calls for a system that has more in common with competing proposals than it has separating them. Like the SPF (Sender Policy Framework) specification, the basic mechanism involves requiring domains that send messages to add records to their DNS that will allow recipients to determine the addresses of the authorized sending servers. Recipients can then see if the sender of a message is really authorized to do so.

SMTP authentications systems like Caller ID wont stop spam in and of themselves, but they will make it possible for reputation systems from vendors such as Brightmail Inc., as well as simpler blacklists and whitelists, to be more effective. With a far smaller amount of spam surviving such challenges, filtering would also become more effective.

Authentication would also put up a huge barrier to e-mail worms like MyDoom, Bagle and Sobig that have comprised the majority of malware attacks in recent years. These worms all use SMTP engines built into the attack code itself. With Caller ID, none of them would authenticate properly in their current form, and its not clear that virus authors would have an effective way to send authenticated mail on arbitrary systems they infected.

There are differences between Caller ID and Sender Policy Framework, but they arent fundamental ones. The format of the records is different, and the method of comparing message headers to those records also differs. There are advantages and disadvantages to both.

At the same time, these differences wont change the basic fact that to implement either standard, owners of e-mail domains will have to upgrade their SMTP mail server (often known as a Message Transfer Agent or MTA) to one that supports the standard. Microsoft should be able to provide this capability in their Exchange Server by means of a plug-in, although its not clear which versions of Exchange they would support. Like SPF, Caller ID would require changes in the Message Transfer Agent to deal with forwarded mail accounts (accounts from which mail is simply moved on to another account, rather than being collected by the users mail client). And like SPF, Caller ID would authenticate just the domain of the sender, not the user within that domain.

With so much in common, why doesnt Microsoft just adopt SPF? According to George Webb, Group Manager of Microsofts Antispam Technology and Strategy Team, the company decided that the differences are important. Next Page: The Differences Between Caller ID and Sender Policy Framework Plans

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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