Force.com provides a multi-level (multi layered ) approach to data security.The following prezi will give you an idea about database security in force.com.

Click on the link: http://prezi.com/kyjrfxga6y-g/1of-1/?auth_key=ce21b574c061ce0c46c009035254691f2643e995&kw=view-kyjrfxga6y-g&rc=ref-20962007

I hope it will be proved useful for the blog readers.

Thank you.