a set of tools called secure-delete exists in ubuntu, and comes with four commands: srm (secure rm), smem (secure wipe from RAM), sfill (fill empty HDD space with random junk), and sswap (clear out swap space). Installation is easy:
sudo apt-get install secure-delete
and you're done! Then you can easily use these tools. Take a look at http://www.techthrob.com/2009/03/02/...rely-in-linux/
, which is where I found this, there is lots more info available.
To delete browser history, a command such as
srm -l ~/.mozilla/"something.default"/places.sqlite
should do the trick, you may need to tailor it slightly to your own environment. The '-l' argument lessens the number of passes to two, makes the command run a little quicker, but less secure. If you want more secure, take out that argument. It will take a long time to run! It is VERY important that you make a bookmarks backup using the Organise Bookmarks menu under Bookmarks in Firefox before running something like this.
BTW, you will need to figure out what the "something.default" directory is on your system.