Attack on SSL Users Discovered, Tool Sources Released
SSL won't come to a rest: the newest attack isn't about encryption or errors in the Secure Sockets Layer protocol, it's about the weakest link in the chain -- the user.
Moxie Marlinspike had already developed sslsniff in 2002. Based on certificate chaining, the client proxy tool intercepts HTTPS traffic from the server and switches the certificate with its own. Assuming a correct configuration and current browser, the result of its use removes any associated attack opportunities. But, asks Marlinspike, what if the client browser doesn't do any SSL queries?
That's why the San Franciscan developed a further proxy named sslstrip (see his presentation slides). The sslstrip tool searches for embedded links, such as https://.../login.php, originating from server webpages and replaces all HTTPS links with like-named HTTP links, such as http://.../login.php, while remembering the original HTTPS target. When the user clicks the modified URL, the sslstrip proxy recognizes it and opens an SSL connection with the server, which sends the webpage, albeit over a nonsecure connection.
In this way the man-in-the-middle (MITM) attacker can access all information from the connection. Such a scenario has an obvious application for online banking where only an HTTP start page might appear, but with visible SSL links and icons that give at least a visual sense of security. Often users ignore warning dialogs and click through them. In the case of an sslstrip intervention, the user doesn't even get the warning dialogs, because no apparent invalid HTTPS connection is created. His browser simply doesn't create a secure connection. The kind of MITM attacks this can provide, and how users might be totally unaware of them, is clearly indicated in Marlinspike's "New Tricks for Defeating SSL in Practice" slides.
After some wide-ranging debate last week about sslstrip, the tool is now available for download. It comprises about 1,000 lines of Python code and is under GLPv3 licensing.
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.

News
-
OpenMandriva Lx 6.0 Available for Installation
The latest release of OpenMandriva has arrived with a new kernel, an updated Plasma desktop, and a server edition.
-
TrueNAS 25.04 Arrives with Thousands of Changes
One of the most popular Linux-based NAS solutions has rolled out the latest edition, based on Ubuntu 25.04.
-
Fedora 42 Available with Two New Spins
The latest release from the Fedora Project includes the usual updates, a new kernel, an official KDE Plasma spin, and a new System76 spin.
-
So Long, ArcoLinux
The ArcoLinux distribution is the latest Linux distribution to shut down.
-
What Open Source Pros Look for in a Job Role
Learn what professionals in technical and non-technical roles say is most important when seeking a new position.
-
Asahi Linux Runs into Issues with M4 Support
Due to Apple Silicon changes, the Asahi Linux project is at odds with adding support for the M4 chips.
-
Plasma 6.3.4 Now Available
Although not a major release, Plasma 6.3.4 does fix some bugs and offer a subtle change for the Plasma sidebar.
-
Linux Kernel 6.15 First Release Candidate Now Available
Linux Torvalds has announced that the release candidate for the final release of the Linux 6.15 series is now available.
-
Akamai Will Host kernel.org
The organization dedicated to cloud-based solutions has agreed to host kernel.org to deliver long-term stability for the development team.
-
Linux Kernel 6.14 Released
The latest Linux kernel has arrived with extra Rust support and more.