Error: Local admin can access my WSS sites

A user who has not been permitted access to the content in your Windows SharePoint Services Web sites has full access to this content. The user can visit any Web page in all your Windows SharePoint Services Web sites. Because of the security requirements in your organization, you may not want all the members of the local Administrators group to have this access. 

Here is the hotfix from Microsoft:

http://support.microsoft.com/kb/892295/