Hello, everyone.
Can you recommend me any whitepaper, redbook or any idea about how to harden a flashsystem?
Thanks in advance.

Hi Alejandro,

You can read Chapter 12 of Implementation Guide Redbook. Also you can check out the Security Concepts on IBM Docs. Lock the superuser and use the Two-Person Integrity and multi-factor authentication features, etc. My favorite is the Two-Person Integrity, and I have a video showing how to configure and use it. you can access the video on this link 

Thanks for your help Nezih.