CREATE TRIGGER ltAdminsOnly
ON ALL SERVER WITH EXECUTE AS N'sa'
FOR LOGON
AS
BEGIN
    Declare @IsAdmin int;
    Exec As login = ORIGINAL_LOGIN();
    Select @IsAdmin = ISNULL(IS_MEMBER('Domain\AdminGroup'), 0);
    Revert;

    If HOST_NAME() <> @@SERVERNAME
        And HOST_NAME() <> SERVERPROPERTY('ComputerNamePhysicalNetBios')
        And @IsAdmin = 0
      Begin;
        ROLLBACK;
      End;
END;