How Secure Is Firefox?

how secure is mozilla firefox
Mozilla's open source Firefox browser has made a significant dent in Internet Explorer's dominant market share. Much of its popularity is due to the wide availability of third-party add-ons that significantly extend Firefox's functionality -- allowing Firefox to disable Java or JavaScript on the fly, perform JavaScript whitelisting, even host ActiveX controls, for example. Firefox has always pushed the boundary in terms of features and functionality, and it can boast both growing enterprise support and the ability to run on Windows, Mac, and Linux. One claim Firefox can't make is a high granularity of security control.

(See related article: How Secure is Google Chrome)

Firefox does not automatically ask for elevation when installing, so be sure to run as administrator beforehand if you want it to install the browser into the normal Program Files folder in Windows Vista or another user-securable location. If installed on Vista, Firefox runs as a single process (Firefox.exe) with medium integrity, DEP (Data Execution Prevention) and ASLR (Address Space Layout Randomization) enabled, and file system and registry virtualization disabled. The latter is a feature in Vista that allows users to run applications without having administrative privileges.

Like Google Chrome, Firefox has a JavaScript engine that converts JavaScript source code into native machine code; Firefox uses an open source engine called TraceMonkey. Unlike Chrome, in which the V8 JavaScript engine is always on, Firefox's JavaScript support can be enabled or disabled across the browser. By using the NoScript add-on, you can enable JavaScript (and Java and Flash) on a per-site basis.

Although add-ons such as NoScript, and plug-ins such as Adobe Flash, bring many useful capabilities to Firefox, at the same time they come with problems and security issues of their own. Firefox has a built-in add-on manager that allows you to browse available extensions, install and uninstall them, and enable and disable them, but again, they can't be enabled or disabled with per-site granularity.

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