How to Hack Your Firefox User Agent to Spoof Your OS and Browser

Nov 8, 2011 06:46 PM

Oct 15, 2019 02:00 AM

There are a lot of things on your computer that can reveal information about you when you are surfing the Internet. If you are like me, then you will do anything to maintain your privacy and prevent those little leaks of information from happening. Here's a list of a few of the "threats" that can reveal information about you:

Undeleted cookies
User Agent
OS fingerprint
IP address
Username (if they pertain to your real name)

For the next few days at Null Byte, we are going to mitigate as many of the Internet's anonymity issues as we can through some safe practices, browser plugins, hacks and more! Today we are going to hack our Internet browser's user agent to appear on websites as a different operating system and browser.

Requirements

Firefox web browser
Any OS

A user agent is something used by JavaScript for a multitude of reasons. Here are just a few of the things that it can be used for:

What Is a User Agent Used For?

Running different versions of a page, based on browser and compatibility with said browser.
Seeing which OS you have to stream media.
Web logs. Someone can use a user agent to identify a hacker via matching logs.
Browser-specific applications compatibility checking.
Marketing sites can use your agent to tailor ads towards you.

Hack Your User Agent

Now, let's actually hack out our agent. I want to have our agent display us as a microwave oven. This ought to throw off the pesky feds after I "r00ted their b0x3n" (just kidding).

Open up Firefox, and in a new tab type:

about:config

In that new tab, click "I'll be careful, I promise!" to proceed.

Type in the search bar on top:

agent

Then find the string value that corresponds to your computer's information. If should look something like this:

Mozilla/5.0 (Windows NT 6.1; rv:5.0) Gecko/20100101 Firefox/5.0

Right-click this value and modify it to display whatever you would like. Here's a silly picture of mine after checking it on Who is Hosting This's User Agent tool.

Funny, isn't it?

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The next big software update for iPhone is coming sometime in April and will include a Food section in Apple News+, an easy-to-miss new Ambient Music app, Priority Notifications thanks to Apple Intelligence, and updates to apps like Mail, Photos, Podcasts, and Safari. See what else is coming to your iPhone with the iOS 18.4 update.