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Pretty is as pretty does

By Scott Bradner

Mark Gibbs likes pretty email. Or so his May 27th column would have us believe. But I hope that he will not send me pretty email when he sees this column because he will get the letter back unread.

I do not know who came up with the idea of using HTML, the protocol used to describe the appearance of web pages, in email but it seems to have been done without much consideration as to the privacy and security implications of doing so.

HTML email can sure be pretty, or is that pretty annoying? The program that Mark gives such a high gear ratio to sounds like it could do quite a nice job of putting together an email message, complete with colors and sound effects, that I would not want to get 1st thing in the morning. But the reason that Mark, or anyone else who sends me an HTML message, will get it automatically tossed back to them has nothing to do with the fact that the mail might contain a tinny version of the "Ride of the Walkure." I bounce HTML-based email because it is a threat to the security of my computer and to my privacy.

This column is far too short to list all the ways that HTML can be a security or privacy threat -- Google gets 77 thousand hits for 'privacy + "html email"' and 20 thousand for 'security + "html email" ' -- but here are a few.

The Computer Emergency Response Team (CERT) has posted a dozen or so warning of ways that HTML email can be used to exploit vulnerabilities in buggy software. Some of the exploits are quite impressive -- see the CERT web site (www.cert.org) for more information.

But the big threats do not depend on flaws in software to work -- they operate even if the software is totally bug-free because they use features in HTML. Kiss your privacy, what shreds you still might have left on the Internet, goodbye if you or your company accepts HTML email.

The sender of the HTML email can find out when and on what computer you read the email. They can find out if you forward the email to someone else, and can find out who the someone else is and return a copy of the cover letter you sent them. The same is true if that someone replies to you or forwards the email to a third person and remains the case as long as the original email is included. They can stick a cookie including your email address on your machine that can later be read by cooperative web sites, even if you are trying to be anonymous.

There are many more threats and I could go on, but you get the not so pretty picture. Sorry Mark, I give the idea of HTML email a minus 9.

disclaimer: This time of year, as part of its fund raising effort, Harvard is very pretty, but has expressed no opinion on pretty email.