UltraSurf Firefox is an add-on for Mozilla Firefox that lets you browse the Internet anonymously; this way you can keep your privacy and security.
The UltraSurf Firefox add-on has three functions: one to hide your IP address so that no one can detect your presence; two to eliminate all the traces you leave behind after browsing (logs, temporary files, cookies, etc); and three, you can apply a filter to the data you send via the Internet so that it is encrypted and no one can detect it or read it.
UltraSurf Firefox is totally free.