BuzzPCSOS I suppose it depends just how big you want your tinfoil hat to be.
Exactly. That's why I asked, "what level of privacy are you trying to obtain?", in my first reply. His answer was, "no agency is investigating me". This thread has taken off, powered by a lot of assumptions.
A question I should have thought of at the time, but didn't until later is, "Do you want to keep and continue using the disk?". If the answer is "No, I'm throwing it away," then many types of blunt-force trauma might do the job quickly. Mgsurya made no mention of an SSD, so I assumed that by "hard disk," he meant it was a disk drive. Those contain neodymiun magnets that are fun to play with, and discs that can be scratched easily, rendering them pretty useless. For an SSD that's to be discarded, nearly any tool from your toolbox will do the job.
On the other hand, if the answer is, "yes, I'm going to keep using it, but I just want the financial data gone", that takes me back to my original suggestion of bleachbit. It's free, it's in the Solus repo, I understand that it works well, and someone who uses it might need to confirm this, but I believe it can be used selectively. E.g., just remove the financial data, but leave the birthday pictures, etc.
