URL Obscuring COEN 252 Computer Forensics  Thomas Schwarz, S.J. 2006

URL Obscuring Internet based criminal activity that subverts web technology: Phishing (fraud) Traffic redirection Hosting of illegal sites Child pornography

URL Obscuring Internet based fraud is gaining quickly in importance. Phishing: The practice of enticing victims with spoofed to visit a fraudulent webpage.

URL Obscuring Technical Subterfuge: Plants crimeware onto PCs. Example: Vulnerable web browser executes remote script at a criminal website. Just staying away from porn no longer protects you. Payload: Use Trojan keylogger spyware. Search for financial data and send it to an untraceable address

URL Obscuring Social Engineering: Target receives 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 to send harvested information to an untraceable account, etc. Connect through public networks.

URL Obscuring: Phishing Example Visible Link: Actual Link: Actual website IP: 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 no longer possible in latest browsers Other techniques to hide web-server address Use hosts file Hiding illegal web-server at legal site Hijacking site to host pages.

URL Basics Phishs can use obscure features of URL. URL consists of three parts: Service Address of server Location of resource.

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.

Obscuring URL Addresses Embed URL in other documents Use features in those documents to not show complete URL URL rules interpret this as a userid. Hide this portion of the URL.

Obscuring URL Addresses Use the password field. has IP address Some browsers accept the decimal value 129*256** *256**2 + 2* = for the IP address. Works as a link. Does not work directly in later versions of IE

Obscuring URL Addresses works. Hide the ASCI encoding Or just break up the name: Or use active page technologies (javascript, …) to create fake links.

Obscuring URL Addresses IDN – International Domain Names Non-english Unicode characters are encoded as basic ASCII strings: punycode punycode example bűcher.ch encoded as xn- - bcher – kva.ch Homographs: Characters from different alphabets look the same Potential URL Obscuring Register paypal.com, where one ‘a’ comes from a different alphabet.

Obscuring URL Addresses Padding URLs.. means go up create directory … /.../../.../../.../../.../error.html

Obscuring URL Addresses Redirection Direct target redirects to main site Chances of main site getting shut down is less Technologies Page-based redirection Add meta tag to head section Server-based redirection Apache: httpd.conf with a redirect statement Redirection via vulnerable websites 2006 eBay run a script that redirected based on query string to any site.

'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

Phishing Phishers now use bogus https techniques. Exploiting browser flaws to display secure icon. Hacking legitimate sites or frames from these sites directly. Purchase and present certificates for sites that are named in resemblance of the target sites. The SSL lock icon is no longer a guarantee for a legitimate site.

Hiding Hosts Name Look-Up: OS checks HOST file first. Can use HOST file to block out certain sites adservers Affects a single machine. OSLocation Linux/etc/hosts Win95/98/MEC:\windows\hosts Win NT/2000/XP ProC:\winnt\systems32\etc\hosts Win XP HomeC:\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 . For example, they can be sent to a free 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.