Again, I really don't recommend changing your DB prefix because it's a risky endeavor and doesn't improve security. It's like removing the www prefix from your website and changing it to 'hidden' in the hope that a hacker won't find you.
There seems to be a lot of misunderstanding around this e.g. @andrezasv you are under the impression that this somehow relates to hiding that you're running WordPress and it's completely unrelated.
I agree with @Barnez regarding changing your admin username, hiding your WordPress version (Wordfence does this), throttling login attempts and the ability to block them (Wordfence does this).
Also agree with @Barnez regarding not changing your folders.
What you want to be doing is running a fairly standard system that will be compatible with any themes and plugins you use, but is also rock solid secure, and you can get that with Wordfence.
Regards,
Mark.