mailing list archives
Re: state of homograph attacks
From: Simon Roberts <thorpflyer () yahoo com>
Date: Sun, 6 Feb 2005 19:49:09 -0800 (PST)
FYI, in case anyone hadn't worked it out yet, the
provided demo works against Konqueror 3.2.1 on KDE
3.2.1 on Suse Linux too.
Pasting the given URL into vi doesn't show the
problem, but view page source (which brings up the
page in KWrite) and "od -xc" do expose the attack.
--- fulldisclosure () cubesearch com wrote:
The state of homograph attacks
International Domain Name [IDN] support in modern
attackers to spoof domain name URLs + SSL certs.
In December 2001, a paper was released describing
Homograph attacks .
This new attack allows an attacker/phisher to spoof
the domain/URLs of
businesses. At the time this paper was written, no
implemented Unicode/UTF8 domain name resolution.
Fast forward to today: Verisign has championed
International Domain Names
(IDN) . RACES has been replaced with PUNYCODE
. Every recent
gecko/khtml based browser implements IDN (which is
just about every
browser  except for IE; plug-in are available
III. The details
Proof of concept URL:
Clicking on any of the two links in the above
webpage using anything but
IE should result in a spoofed paypal.com webpage.
The links are directed at
"http://www.p?ypal.com/", which the
browsers punycode handlers render as
This is one example URL - - there are now many ways
to display any domain
name on a browser, as there are a huge number of
look very similar to latin charsets.
Phishing attacks are the largest growing class of
attacks on the internet
today. I find it amusing that one of the large
early adopters of IDN
offer an 'Anti-Phishing Solution' .
Finally, as a business trying to protect their
identity, IDN makes their
life very difficult. It is expected there will be
many domain name
related conflicts related to IDN.
Vulnerable browsers include (but are not limited
Most mozilla-based browsers (Firefox 1.0, Camino
.8.5, Mozilla 1.6, etc)
There are some inconsistencies with how the browsers
match the host name
with the Common Name (CN) in the SSL cert. Most
browsers seem to match
the punycode encoded hostname with the CN, yet a few
(try to) match the
raw UTF8 with the CN. In practice, this makes it
impossible to provide
'SSL' services effectively, ignoring the fact that
IE doesn't yet support
There are a few methods to detect that you are under
a spoof attack. One
easy method is to cut & paste the url you are
accessing into notepad or
some other tool (under OSX, paste into a terminal
window) which will allow
you to view what character set/pagecode the string
is in. You can also
view the details of the SSL cert, to see if it's
using a punycode wrapped
version of the domain (starting with the string
You can disable IDN support in mozilla products by
'network.enableIDN' to false. There is no
workaround known for Opera or
VI. Vendor Responses
Verisign: No response yet.
Apple: No response yet.
Opera: They believe they have correctly implemented
IDN, and will not be
making any changes.
Mozilla: Working on finding a good long-term
solution; provided clear
workaround for disabling IDN.
2002 - Original paper published on homograph attacks
2002-2005 - Verisign pushes IDN, and browsers start
adding support for it
Jan 19, 2005 - Vendors notified of vulnerability
Feb 6, 2005 - Public disclosure @shmoocon 2005
This paper is copyright 2005, Eric Johanson
ericj () shmoo com
Assistance provided by:
- The Shmoo Group
- The Ghetto Hackers
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