On Sep 3, 2009, at 12:26 AM, Peter Gutmann wrote:
Steven Bellovin <s...@cs.columbia.edu> writes:
This returns us to the previously-unsolved UI problem: how -- with
today's
users, and with something more or less like today's browsers since
that's
what today's users know -- can a spoof-proof password prompt be
presented?
Good enough to satisfy security geeks, no, because no measure you
take will
ever be good enough. However if you want something that's good
enough for
most purposes then Camino has been doing something pretty close to
this since
it was first released (I'm not aware of any other browser that's
even tried).
When you're asked for credentials, the dialog rolls down out of the
browser
title bar in a hard-to-describe scrolling motion a bit like a
supermarket till
printout. In other words instead of a random popup appearing in
front of you
from who knows what source and asking for a password, you've got a
direct
visual link to the thing that the credentials are being requested
for. You
can obviously pepper and salt this as required (and I wouldn't dream
of
deploying something like this without getting UI folks to comment
and test it
on real users first), but doing this is a tractable UI design issue
and not an
intractable business-model/political/social/etc problem.
Several other people made similar suggestions. They all boil down to
the same thing, IMO -- assume that the user will recognize something
distinctive or know to do something special for special sites like
banks. Both, to me, are unproven assumptions. Worse yet, both the
security literature and what I've seen of user behavior strongly
suggest to me that neither scenario is true.
Peter, I'm not sure what you mean by "good enough to satisfy security
geeks" vs. "good enough for most purposes". I'm not looking for
theoretically good enough, for any value of "theory"; my metric -- as
a card-carrying security geek -- is precisely "good enough for most
purposes". A review of user studies of many different distinctive
markers, from yellow URL bars to green partial-URL bars to special
pictures to you-name-it shows that users either never notice the
*absence* of the distinctive feature or are fooled by a tailored
attack (see, e.g., the paper on picture-in-picture attacks). Maybe
Camino is really better -- or maybe it just hasn't been properly
attacked yet, say by a clever flash animation or some AJAX weirdness.
Given the failure of all previous attempts -- who, amongst the
proponents of EV certificates, realized that attackers could and would
use all-green favicon.ico files to fool users -- I think the burden of
proof is on the proponents.
--Steve Bellovin, http://www.cs.columbia.edu/~smb
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