Security firm zScaler have released a new Firefox plug-in, BlackSheep, in hopes of combating attempts by those using FireSheep to try to hijack their Web session. The tool doesn t protect users from being hijacked, but does alert them when Firesheep is being used on a network they re currently logged onto. The plug-ins are just the latest attempt to protect Web users on unencrypted wireless networks against prying eyes. An earlier release, FireShepherd, attempts to disrupt FireSheeps s attempts to listen in on insecure Web sessions.
Source: https://threatpost.com/blacksheep-plugin-bites-back-detecting-firesheep-hijack-attempts-110810/74651/