"It was written" is a past simple passive form. "It has been written" is a present perfect passive form. We use "it was written" when talking about a text (a poem, book, novel, story, etc) whose writer is dead, while we use "it has been written" when talking about a text whose writer is still alive. For example, "The Chimney Sweeper" was written by William Blake. The English poet William Blake is not alive, so we use past simple passive (or past simple) form when talking about his literary works.

They are different. 'Was' is past tense and 'Has been' is present perfect continous tense. Instead of explaining with examples, I thought this link might help you to understand use of 'has been' better. Please refer: http://www.englishclub.com/grammar/verb-tenses_present-perfect-continuous.htm. Use of 'was' happens when we refer to an action that is completed (or refer to certain past event).