What happends when you give 2 groups with some of the same members different authorizations for a document

Question

Hello,
I'm doing my internship at a litte Telekom company. I'm investigating how they can use MS SharePoint as their central place to put projectinformation. Now i've been thinking what happends when i do the following:
Make one document library
Add 2 groups to the Active Directory, group "A" with all the employees and group "B" with only four people working on a project. When i add a document to the document library and set the authorizations for the document as
follows:
Group B: Read/Write
Group A: Read
Does the people from group B still be able to edit the document, because they are also in group A?
I don't have a test environment to test this myself.
Why i want to know this? The company want's one place to place all their documents with projectinformation. This information is about different projects. You only wan't that people can change the specific document when they are working on the specific project
where the document belongs to.  

Answer 1

You get the union of permissions, so if one group allows access and the other not, you will get the union of both and therefore access. Of course, you can break security settings per library/folder or document, and specify new settings,
if you need too.
Kind regards,
Margriet Bruggeman
Lois & Clark IT Services
web site: http://www.loisandclark.eu
blog: http://www.sharepointdragons.com