Application Layer Gateway Service (ALG) Defaults in Windows 7

Provides support for 3rd party protocol plug-ins for Internet Connection Sharing.

Default Settings

Startup type: Manual
Display name:Application Layer Gateway Service
Service name:ALG
Service type:own
Error control:normal
Object:NT AUTHORITY\LocalService
Registry key:HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ALG
  • SeChangeNotifyPrivilege
  • SeCreateGlobalPrivilege
  • SeImpersonatePrivilege

Default Behavior

Application Layer Gateway Service is a Win32 service. In Windows 7 it won't be started if the user doesn't start it. When the Application Layer Gateway Service is started, it is running as NT AUTHORITY\LocalService in its own process of alg.exe. If Application Layer Gateway Service fails to start, Windows 7 attempts to write the failure details into Event Log. Then Windows 7 startup should proceed and the user should be notified that the ALG service is not running because of the error.

Restore Default Startup Configuration of Application Layer Gateway Service

1. Run the Command Prompt as an administrator.

2. Copy the command below, paste it into the command window and press ENTER:

sc config ALG start= demand

3. Close the command window and restart the computer.

The ALG service is using the alg.exe file that is located in the C:\Windows\System32 directory. If the file is removed or corrupted, read this article to restore its original version from Windows 7 installation media.