Hilchos Lashon Hara chapter 10, section 13

However, I think it is allowed if you expect that telling people how someone wronged you in money and the like will bring a benefit.

For example:

- You tell people the wrongdoer will listen to, so that he returns what he took.

- He is about to shame you unfairly, and you tell important people or his friends the truth, so they stop him.

- He already shamed you, and you want to stop it from happening again, so you tell his friends or important people.

This is allowed because your goal is to protect yourself.