A Firefox profile stores all personal information such as bookmarks and passwords in it. Everyone who is starting up Firefox with that profile is able to use your saved passwords and cookies as well which is a security risk if you ask me. One way to overcome this would be to protect the Firefox profile folder by moving it to a location that is not accessible to anyone except you.
I did this by moving the profile to my encrypted hard drive. The hard drive is encrypted using True Crypt and the profile can only be accessed if I provide the security key to decrypt the hard drive. Other means are theoretically possible as well, use a portable device that has to be plugged in before you can use the profile.
Moving a profile to another location is not difficulty at all. Close all instances of Firefox and locate your profile folder. This is usually in Document and Settings under Application Date, Mozilla, Firefox, Profiles of the user who is logged into windows currently.
Move the complete folder to a different location. Open up profiles.ini afterwards (located in Firefox in Document and Settings). Change the path= parameter to the new location of your profile and change the parameter IsRelative=1 to 0.
Restart Firefox to see if the changes have been made. If all your bookmarks for instance load fine the changes have been successful. If that is not the case double-check the path parameter in profiles.ini.

How to move the bookmarks in Firefox 3
Move Thunderbird Email Profiles To Another Location
Working with several Firefox profiles
Moving The Firefox Disk Cache To Another Drive
If the goal is to protect yourself from childs or mother, this extension : https://nic-nac-project.de/~kaosmos/profilepassword-en.html#PPFF
can do the trick… It’ll set a password to open your profile…
But it’s really easy to bypass, so not as reliable as TrueCrypt…
Great trick and easy to put in practice.
Hello,
I’m a little “general-purpose” IT-consultant. One of my goals is to analyze and manage (may be improve) medium size business’ everyday work.
The first problem is that my customers hove no idea of the main series of risks.
First: protect THEIR CUSTOMERS sensitive data. There are severe law restrictions to manage sensitive data in Italy, so my customers are continuously in front of high risk.
In case of theft of hardwares they are completely exposed, but also when they are connected to the Internet. (”Firewall? What’s a firewall? we have fire extinguishers!” or “Get rid of all those annoying popups or you can go home!”).
I had already thought about this solution, TrueCrypt is my first choice for my own problems, but not so accessible to non-power-users…
First problem: by default old Mozilla profile manager is hidden in mff, and has to be launched by command prompt in windows…
Very old version of mozilla and netscape required password to access a profile, but I’m not able to find whether were there encryption of profiles’ data.
Does anyone know whether are there integrated solutions for password-protect and encrypt profiles in Firefox and Thunderbird?
[The problem is almost identical in Opera (don't tell me nothing about M$IE)]
I mean open-source, or if not, commercial too…
Or we can go further: are there other browser I don’t know yet?
Thanks a lot,
Luca