The accounts that you add to the ArcGIS Server users group, agsusers, are those users who you expect to access the services over local area network (LAN) connections. The accounts that your Web applications run as should also be in this group. These users will not be able to administer the GIS server.
Don't worry if you don't have the complete list of accounts. You can always add and remove accounts later.
1. On the SOM machine, start the Computer Management application. Computer Management can be found in the Control Panel under Administrative Tools.
2. Expand System Tools, then Local Users and Groups, then Groups.
3. Right-click the ArcGIS Server users group, named agsusers, and click Properties.
4. On the Property page, click Add and, in the dialog box that appears, add those operating system accounts to which you want to grant access to the GIS server. These are typically the accounts that people use to log in to the network from their own computer. Note: You don't need to add administrative users to this group. Administrative users already have user-level privileges to the services.
5. Repeat steps 1 through 4 on each server object container machine.
The users of the accounts you add to the ArcGIS Server users group may need to log off and back on before the new settings take effect.