If you’re really serious about not being followed on the Internet your choice is the Tor browser, which leverages a network of virtual tunnels to improve security and privacy. This week the Tor Project released version 4.0.4, which is based on Mozilla Firefox 3.15 browser.

Separately Firefox released version 36 of its browser with fixes for a number of vulnerabilities.

Tor, used by security researchers, IT professionals, software developers, reporters and activists — as well as by hackers and criminals on the Dark Web —  protects the transport of data so users can’t be tracked.

The new features include updates to Firefox 31.5.0esr,  OpenSSL to 1.0.1, NoScript to,  and HTTPS-Everywhere to 4.0.3

There are also three bug fixes: 14203, which prevents meek from displaying an extra update notification; 14849, which removes a NoScript menu option to make permissions permanent; and 14851, which sets NoScript pref to disable permanent permissions.

If you haven’t used the Tor browser before note that it blocks plugins like Flash, RealPlayer and Quicktime because they can reveal IP addresses.

As a tool that can help — and hinder — security the Tor network is an obvious target for people who don’t like it or want to know who’s on it. For example, last December The Hacker News reported the Tor Project warned users it had learned of an attack on its directory authorities.

Mozilla works with the Tor Project, most recently in January when, working with the Center for Democracy and Technology on an initiative called Polaris, it gave the network 12 high-capacity middle relays to help reduce finite number of Tor connections occurring at the same time.

In its version 36 release of Firefox, Mozilla said it fixed three critical vulnerabilities: a buffer overflow in libstagefright during MP4 video playback; a use-after-free vulnerability; and what it calls miscellaneous memory safety hazards.