Hi QNAP, I need help, I'm looking for a way to...

Hi QNAP, I need help, I'm looking for a way to secure erase the free space on my Qnap TS-859, Configured in 2 x raid 5 arrays. I cant seem to find and app or any information that would allow this, I would also like a way to secure erase files, as the free space / files are easily recovered with many apps and i don't want this.
 
Hi Sir, to provide you more accurate assistance, please submit a ticket to QNAP Helpdesk -. Our tech support agents can help you. Thank you.