The first thing that you need to do is to confirm that the news that you have is true and the source of the news is authentic. At times, such news is a result of gossip and there is little truth to it. You need to confirm it before you proceed in dealing with it. At times, a long flow of communication distorts the original message and develops a misunderstanding.
Confront your friend in a light manner and allow him to explain himself honestly. You need to give him a chance to explain himself honestly. However, if the answer is unsatisfactory, you can be sure that he did it intentionally, you can respond in a befitting manner.
The one effective treatment you can give your backstabber friend is the silent one. Ignore him and cut him off from the group of friends. Try to repay him with social isolation if you are feeling revengeful. Discourage mutual friends from interacting with him by taking them in to confidence with the situation. If friends know that he can do to them what he has done to you, they will not trust or believe him.
A revenge for a backstabbing friend will be to do the same to him. We all know that forgiving is better than revenge but what about someone who has done it deliberately and has no remorse. Spread as much mischief about him as possible so that he feels the pain that he has caused you. It will help to forget that you were ever friends. If he has misused your secrets, you can do the same to him. There is no use of continuing friendship with such a person because there is no trust element remaining, without which relationships cannot last.