Running services under a LocalSystem account can be dangerous, because LocalSystem is essentially Administrator and, therefore, has access to virtually any resource on the machine. Design flaws or buggy code in a service running under LocalSystem might result in an escalation of privilege for a destructive user. Windows XP introduced two new built-in service accounts, LocalService and NetworkService, specifically designed to mitigate the consequences of a service compromise. These two new accounts are restricted user accounts without any special privileges, except "Login as service".
In keeping with this security initiative, the WIA service runs under the LocalService account in Microsoft Windows Server 2003 and later operating system versions.
Prior to Windows Server 2003, the WIA service and WIA drivers were developed on the assumption that they would run under LocalSystem. This changed with Windows Server 2003 and has several ramifications that driver developers need to be aware of. This section contains a list of common problems that a WIA driver developer might experience, including possible ways to resolve them.
Following the practices outlined in this document ensures that the WIA drivers developed will function correctly whether running on Windows XP, Windows Server 2003, or later operating system versions.