How exactly miners to provide protection?

I don't really understand what you are asking, can you clearify your question?

i think it was something like "exactly how miners provide the system security?"

OP:

you need to google about proof of work systems and "what the proof of work is?". In two works - block of tranaction considered liquid if there are some "signature". This sign is the answer on difficult math task. So miners trying to solve this task and make some block of transaction liquid. And getting the reward (25 btc) for solving the problem. Something like that