discussion board Security in SharePoint

We have created a discussion board in Office SharePoint Server 2007 (MOSS).
The system allow users to add new post and it also allows other users to edit
the first posted topic. What security that I should create and provide that
will allow only the owner to modify his or her post.
Thank you for your help,
G

You have to make changes in the list's settings.

You have to make changes in the list's settings. Go to Settings  > Advanced
Settings. In "Item level permissions" change "Edit Access" to "Only their
own". Give users read and write permissions.

discussion board Security in SharePoint

Thank you SSA.