Subject: [Asrg] News Article - C/R systems and mailing lists

From: Yakov Shafranovich <[email-masked]>
Date: Tue, 27 May 2003 12:48:23 -0400

Here is a news article on the impact of C/R systems on mailing lists:

http://news.com.com/2010-1071-1009745.html

Interesting quote:

" Fortunately, the Internet Engineering Task Force's Anti-Spam Research 
Group is spending some time trying to devise a reasonable standard. "

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Spam blockers may wreak e-mail havoc
By Declan McCullagh
May 27, 2003, 4:00 AM PT

Here's an unhappy prediction: The explosion of spam-blocking technology 
could herald the death of much legitimate e-mail.

I wrote about patents relating to this technology, known as 
challenge-response technology, last week. Basically, when your mailbox is 
protected by a challenge-response system, people who try to contact you 
will be greeted with a response saying something like "click on this link 
to deliver this message" or "type in the word you see in the box above." 
The idea is to block increasingly obnoxious spam bots but still let actual 
humans get in touch with you.

In theory, well-designed challenge-response utilities won't challenge mail 
from known correspondents or mail that you've actually asked to receive. 
Unfortunately, many current challenge-response systems are poorly designed, 
which could wreak havoc on mailing lists and other legitimate 
communications. This could make e-mail far less useful than it is today.

It's already starting to happen. SpamArrest.com began challenging mailing 
list messages last year. Recently Mail-block.com and iPermitMail.com 
followed suit.

When that happens, the operator of the mailing list receives a 
message--from each subscriber using the poorly designed challenge-response 
utility--that asks the list operator to respond to the challenge. Replying 
to a handful of challenges is no big deal, but if many subscribers start 
using poor challenge-response software, it will pose a serious problem for 
mailing list operators. Big corporations may be able to afford to hire 
someone to sit in front of a computer and spend all day proving they're not 
a spam bot, but nonprofit groups, individuals and smaller companies 
probably can't.

Challenge-response systems, ironically, share some characteristics with 
spam: In small quantities, both are only mildly annoying to the recipient. 
But as quantities increase, they make it more difficult to use e-mail at 
all. MailFrontier.net is a good example: It prevents its users from signing 
up to mailing lists unless the list operator manually intervenes to answer 
the challenge, a process that is exactly backward.

The enormous growth in spam means that challenge-response technology will 
become more popular. EarthLink recently announced it would make a 
challenge-response system available to its customers by the end of May, and 
the field is wide open, with no market leader so far.

EarthLink's announcement has alarmed veteran list operators, who view it as 
a model that other Internet service providers may follow. Dave Farber, the 
University of Pennsylvania computer scientist who runs the "interesting 
people" list, warned his subscribers: "If I start getting a flood of 
challenges from EarthLink IPers that require my response I will most likely 
declare them spam and you will stop receiving IP mail. I fully expect this 
to be the case for almost all the legitimate mailing lists you are on and 
count on."

This could make e-mail far less useful than it is today.
Editors at TidBits, the popular Macintosh newsletter that boasts about 
50,000 subscribers, wrote a message on May 13 to readers: "Be warned that 
we will not answer any challenges generated in response to our mailing list 
postings. Thus, if you're using a challenge-response system and not 
receiving TidBits, you'll need to figure that out on your own."

It's worth remembering that, while they may not be as glamorous as the Web, 
peer-to-peer applications, or instant messaging software, mailing lists are 
the Internet's oldest form of mass communication. They date back to the 
original "MsgGroup" list in 1975, which the same Dave Farber--then at the 
University of California at Irvine--helped to create. Then the famous 
"sf-lovers" list came along, and the rest is, well, history.

Nowadays just about every organization uses mailing lists of some type, 
from Hotwire.com's cheap airfare announcements to the left-leaning 
activists at MoveOn.org who organized a massive e-mail campaign against the 
Iraq war. Professional organizations use them to contact members; companies 
offer deals to existing customers; and advocacy groups rely on lists to 
rally support for political causes. And that's not counting services like 
Yahoo Groups and Topica.

Another downside to challenge-response systems is that they can be 
exploited by spammers, yielding false negatives in addition to false 
positives. Some challenge-response systems require only that the sender 
reply to the challenge; others require only that a hyperlink in the 
challenge be followed.

A more pernicious problem is that challenge-response systems trust the 
"From:" line of a message. If challenge-response systems become 
sufficiently widespread, spam bots may start trying to guess at who your 
correspondents are--and then forge the "From:" header appropriately--by 
subscribing to discussion lists or following links from your personal or 
company home page. Digital signatures are probably the only way to prevent 
that kind of attack.

John Levine, an author, moderator of the comp.compilers Usenet newsgroup 
and veteran Internet hand, offers a gloomy worst-case prediction. "So what 
will the effect of this be?" Levine asks. "You won't be able to trust that 
mail from your friends is actually from your friends, since an increasing 
fraction will be spam leaking through your challenge system. What will 
people do? Given the basic principle of challenge systems, which is that 
it's someone else's job to solve your spam problem, people will dump their 
white lists and start challenging every message."

At least right now, because challenge-response systems are so easy for 
programmers to create, there are plenty of them, and the potential for 
market dominance has attracted some companies of dubious virtue. SpamArrest 
spammed advertisements to people who e-mailed its customers (imagine if AOL 
or MSN claimed the right to spam anyone who's ever sent you mail). 
Mail-block.com has been blocked by Outblaze.com, a large mail provider, for 
spamming. And MailWiper.com has been caught spamming.

For a challenge-response system to work properly, it will need to be 
tightly integrated with the mail client--so it knows who you contacted--and 
it should understand popular mailing list software such as Majordomo, 
Mailman and Listserv. It's easier for challenge-response companies that 
sell Web-based e-mail. For people using software like Eudora and Outlook, 
that probably means plug-ins or an e-mail proxy server that let the 
challenge-response system keep track of your outgoing messages.

Brad Templeton, chairman of the Electronic Frontier Foundation and author 
of one of the first challenge-response systems, compiled a useful list of 
design principles for challenge-response systems earlier this month. 
Templeton's list has some recommendations: Never challenge any mail that's 
a reply to a private message you sent; use multiple e-mail addresses; and 
never challenge mailing-list messages.

All these should be obvious, but many challenge-response systems just don't 
follow them. Fortunately, the Internet Engineering Task Force's Anti-Spam 
Research Group is spending some time trying to devise a reasonable standard.

Challenge-response systems may turn out to be the only way to inoculate 
ourselves against the spam epidemic. Or they may not. But their designers 
and users should think twice before trusting the future of Internet e-mail 
to buggy and problematic technology.

  Copyright ©1995-2003 CNET Networks, Inc. All rights reserved.
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