URL Obscuring
COEN 152/252 Computer Forensics
Thomas Schwarz, S.J. 2004
URL Obscuring Internet based fraud is gaining quickly
in importance. Phishing: The practice of enticing
victims with spoofed email to visit a fraudulent webpage.
http://www.antiphishing.org/
Graphics courtesy of Tumbleweed Communications
URL Obscuring Target receives e-mail pretending to be
from an institution inviting to go to the institutions website.
Following the link leads to a spoofed website, which gathers data. It is possible to establish a web-presence
without any links: Establish website with stolen / gift credit card. Use email to send harvested information to an
untraceable account, etc. Connect through public networks.
URL Obscuring: Phishing Example
Visible Link: https://www.usa.visa.com/personal/secure_with_visa/index.html?t=h1_/index.html
Actual Link: http://www.verified-web-us.com/Visa%20USA%20%20Personal%20%20Protect%20Your%20Card.htm
Actual website IP: 209.35.123.41
Uses Java program to overwrite the visible address bar in the window:
URL Obscuring:Phishing Example
URL Obscuring Phishs need to hide web-servers
URL Obscuring Javascript or other active web-
technology overwrites URL field Other techniques to hide web-
server address Use hosts file
Hiding illegal web-server at legal site
URL Basics
Phishs can use obscure features of URL.
URL consists of three parts: Service Address of server Location of resource.
http://www.cse.scu.edu/~tschwarz/coen252_03/Lectures/URLObscuring.html
URL Basics Scheme, colon double forward slash. An optional user name and password. The internet domain name
RCF1037 format IP address as a set of four decimal digits.
Port number in decimal notation. (Optional) Path + communication data.
http://tschwarz:[email protected]/~tschwarz/coen252_03/Lectures/URLObscuring.html
http://www.google.com/search?hl=en&ie=UTF-8&q=phishing
Obscuring URL Addresses
Embed URL in other documents Use features in those documents
to not show complete URLhttp://[email protected]/~tschwarz/coen252_03/index.html
URL rules interpret this as a userid.
Hide this portion of the URL.
Obscuring URL Addresses
Use the password field. www.scu.edu has IP address 129.210.2.1. Some browsers accept the decimal value
129*256**3 + 210*256**2 + 2*256 + 1 = 2178023937 for the IP address.
http://www.usfca.edu@2178023937 Works as a link. Does not work directly in later versions of IE
Obscuring URL Addresses
http://[email protected] works.
Hide the ASCI encoding of @: http://www.usfca.edu%40129.210.2.1
Or just break up the name: http://www.usfca.edu%40%127%167w.scu.edu
Or use active page technologies (javascript, …) to create fake links.
'Enroll your card with Verified By Visa program'
2004 Phish sends SPAM consisting of a single image:
'Enroll your card with Verified By Visa program'
The whole text is a single image, linked to the correct citi URL.
If the mouse hovers over the image, it displays the correct citi URL.
But surrounded by an HTML box that leads to the phishing website.
'Enroll your card with Verified By Visa program'
Target webpage has an address bar that is overwritten with a picture with a different URL.
Go to www.antiphishing.org .
Hiding Hosts Name Look-Up:
OS checks HOST file first. Can use HOST file to block out certain sites
adservers Affects a single machine.
OS Location
Linux /etc/hosts
Win95/98/ME C:\windows\hosts
Win NT/2000/XP Pro
C:\winnt\systems32\etc\hosts
Win XP Home C:\windows\system32\drivers\etc\hosts
Subverting IP Look-Up
In general, not used for phishing. Economic Damage
Hillary for Senate campaign attack. Hiding illegal websites. (Kiddie Porn)
DNS Server Sabotage IP Forwarding
Subverting IP Look-Up Port Forwarding
URLs allow port numbers. Legitimate business at default port number. Illegitimate at an obscure port number.
Screen clicks Embed small picture.
Single pixel. Forward from picture to the illegitimate site. Easily detected in HTML source code.
Password screens Depending on access control, access to
different sites.
Phisher-Finder Carefully investigate the message
to find the URL. Do not expect this to be successful
unless the phisher is low-tech. Capture network traffic with
Ethereal to find the actual URL / IP address.
Use Sam Spade or similar tools to collect data about the IP address.
Phisher-Finder
Capture network traffic with Ethereal when going to the site. This could be dangerous.
Disable active webpages. Do not use IE (too popular).
Look at the http messages actually transmitted.
Expect some cgi etc. script.
Phisher-Finder Investigation now needs to find the
person that has access to the website. This is were you can expect to loose the trace.
The data entered can be transmitted in various forms, such as anonymous email.
For example, they can be sent to a free email account. IPS usually has the IP data of the computer from which
the account was set up and from which the account was recently accessed.
Perpetrator can use publicly available computers and / or unencrypted wireless access points.
Investigator is usually left with vague geographical data.
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