shred
When you really want to delete a file, and make it very hard to recover, shred can come in handy:
shred -u -z -n 10 plan-for-world-domination.txt
The above will overwrite your plan-for-world-domination.txt file with random ones and zeros 10 times, remove the file and finally overwrite it with zeros (in a bid to hide the fact you’ve shredded the file).
Needless to say, shred should be used with caution.
