Specific read write access?

Hi there,
I'm new to a project and the group uses ownCloud to share files. There is only the problem that everyone has the possibility to read and write every file. In the past that caused big trouble. So I wanted to ask if there is an easy way to give certain persons to certain files/ folders only a read and no write permission?
I couldn't find anything about that.
Thank you very much

Yes, when you create a share, you can define CRUDS which means Create, Read, Update, Delete and Share ...