Zscaler Tools

BlackSheep – Firefox Add-on

Add to Firefox
Click on the link above to install the plugin.

Version
1.7.1

Requirements

In order to install BlackSheep, you need:

  • Mac OS X: 10.5 or newer on an Intel processor.
  • Windows: XP or newer. Install Winpcap first!
  • Firefox: 3.5 or newer. 32-bit only.
  • Linux : details here

Description

At the Toorcon 12 security conference, Eric Butler released a Firefox plugin named Firesheep, which drew significant media attention. Firesheep allowed any user to seamlessly hijack the web session of another user on the same local network. Although such attacks are not new, the ease of use presented by Firesheep brought session hijacking to the masses.

BlackSheep, also a Firefox plugin is designed to combat Firesheep. BlackSheep does this by dropping ‘fake’ session ID information on the wire and then monitors traffic to see if it has been hijacked. While Firesheep is largely passive, once it identifies session information for a targeted domain, it then makes a subsequent request to that same domain, using the hijacked session information in order to obtain the name of the hijacked user along with an image of the person, if available. It is this request that BlackSheep identifies in order to detect the presence of Firesheep on the network. When identified, the user will be receive the following warning message:

Fire Sheep

It should be noted that Firesheep and BlackSheep cannot be installed on the same Firefox instance as they share much of the same code base. If you want to run both Firesheep and BlackSheep on the same machine, they should be installed in separate Firefox profiles.

The Problem

Session hijacking is nothing new. Web sites typically use SSL connections for initial login pages, but revert to non-encrypted traffic for all subsequent communication. As such, while a user’s username and password may be protected, once they are authenticated, any user on the same network can simply sniff network traffic, obtain a user’s session ID and then hijack their session for a given website. Although this has always been a serious risk, especially on insecure networks such as public wifi hot spots, some degree of technical knowledge was required to accomplish the attack. Firesheep, opens such attacks to the masses as it turns session hijacking into a point and click exercise. Unless websites mandate SSL for all traffic on the site, session hijacking will always remain a threat. Fortunately, BlackSheep can be used to let you know if someone is running Firesheep on the same network.

Configuration

BlackSheep options can be accessed by navigating to Tools > Add-ons within Firefox. Once there, under the Extensions tab, select the Preferences button for BlackSheep.

Firesheep

Check Interval: BlackSheep will continually drop fake session information onto the wire and then listen for another IP address re-submitting this same information, as this will indicate the presence of Firesheep on the network. The Check Interval identifies the number of minutes between checks.

Interface: Allows the user to configure the network interface that BlackSheep should listen on.

If you find any problem with this add-on, please let me know at jsobrier@zscaler.com

 

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