Defeating SSL using SSLStrip --3rd level hack not for beginners

 

Marlinspike(blackhat) made a great presentation in Blackhat this year on how to subvert SSL (HTTPS) protection used bu major sites around the Internet for security. The interesting thing is that he does not really break the SSL protocol itself, but instead demonstrates that as HTTP is the entry point into any SSL communication, subverting HTTP allows a hacker to take control of the HTTPS communication as well.

Marlinspike also released the SSLStrip tool to automate this attack. Download SSLstrip from Moxie's website or from here. Using the SSLStrip tool Marlinspike was able to retreive over 130 usernames and passwords over a Tor network. These credentials were from sites such as Gmail, Yahoo, Linkedin, Paypal etc.

The way the SSLStrip tool works by:

 1>>Does an MITM on the HTTP connection
2>>Replaces all the HTTPS links with HTTP ones but remembers the links which were changed
3>>Communicates with the victim client on an HTTP connection for any secure link
4>>Communicates with the legitimate server over HTTPS for the same secure link
5>>Communication is transparently proxied between the victim client and the legitimate server
6>>Images such as the favicon are replaced by images of the familiar "secure lock" icon, to build trust
7>>As the MITM is taking places all passwords, credentials etc are stolen without the Client knowing