Local user accounts in Windows
In this post I want to summarize an overview from Microsoft about local accounts in windows.
Local Accounts
https://docs.microsoft.com/en-us/windows/security/identity-protection/access-control/local-accounts
Local user accounts are stored locally on the server. These accounts can be assigned rights and permissions on a particular server, but on that server only. Local user accounts are security principals that are used to secure and manage access to the resources on a standalone or member server for services or users.
Default local user accounts
The default local user accounts are built-in accounts that are created automatically when you install Windows.
After Windows is installed, the default local user accounts cannot be removed or deleted. In addition, default local user accounts do not provide access to network resources.
Default local user accounts are used to manage access to the local server’s resources based on the rights and permissions that are assigned to the account. The default local user accounts, and the local user accounts that you create, are located in the Users folder. The Users folder is located in the Local Users and Groups folder in the local Computer Management Microsoft Management Console (MMC). Computer Management is a collection of administrative tools that you can use to manage a single local or remote computer. For more information, see How to manage local accounts later in this topic.
Default local user accounts are described in the following sections.
Administrator account
The default local Administrator account is a user account for the system administrator. Every computer has an Administrator account (SID S-1-5-domain-500, display name Administrator). The Administrator account is the first account that is created during the Windows installation.
The Administrator account has full control of the files, directories, services, and other resources on the local computer. The Administrator account can create other local users, assign user rights, and assign permissions. The Administrator account can take control of local resources at any time simply by changing the user rights and permissions.
The default Administrator account cannot be deleted or locked out, but it can be renamed or disabled.
In Windows 10 and Windows Server 2016, Windows setup disables the built-in Administrator account and creates another local account that is a member of the Administrators group. Members of the Administrators groups can run apps with elevated permissions without using the Run as Administrator option. Fast User Switching is more secure than using Runas or different-user elevation.
- Get SID of a local user
wmic useraccount where name=’administrator’ get sid - Get SID for current logged in user
wmic useraccount where name=’%username%’ get sid - Get SID for current logged in domain user
whoami /user - Get SID for the local administrator of the computer
wmic useraccount where (name=’administrator’ and domain=’%computername%’) get name,sid - Get SID for the domain administrator
wmic useraccount where (name=’administrator’ and domain=’%userdomain%’) get name,sid - Find username from a SID
wmic useraccount where sid=’S-1-5-21-2593857963-3184534624-523876939-500′ get name
Account group membership
By default, the Administrator account is installed as a member of the Administrators group on the server. It is a best practice to limit the number of users in the Administrators group because members of the Administrators group on a local server have Full Control permissions on that computer.
The Administrator account cannot be deleted or removed from the Administrators group, but it can be renamed.
Security considerations
Because the Administrator account is known to exist on many versions of the Windows operating system, it is a best practice to disable the Administrator account when possible to make it more difficult for malicious users to gain access to the server or client computer.
You can rename the Administrator account. However, a renamed Administrator account continues to use the same automatically assigned security identifier (SID), which can be discovered by malicious users. For more information about how to rename or disable a user account, see Disable or activate a local user account and Rename a local user account.
As a security best practice, use your local (non-Administrator) account to sign in and then use Run as administrator to accomplish tasks that require a higher level of rights than a standard user account. Do not use the Administrator account to sign in to your computer unless it is entirely necessary. For more information, see Run a program with administrative credentials.
In comparison, on the Windows client operating system, a user with a local user account that has Administrator rights is considered the system administrator of the client computer. The first local user account that is created during installation is placed in the local Administrators group. However, when multiple users run as local administrators, the IT staff has no control over these users or their client computers.
In this case, Group Policy can be used to enable secure settings that can control the use of the local Administrators group automatically on every server or client computer. For more information about Group Policy, see Group Policy Overview.
Note Blank passwords are not allowed in the versions designated in the Applies To list at the beginning of this topic.
Important Even when the Administrator account has been disabled, it can still be used to gain access to a computer by using safe mode. In the Recovery Console or in safe mode, the Administrator account is automatically enabled. When normal operations are resumed, it is disabled.
Guest account
The Guest account is disabled by default on installation. The Guest account lets occasional or one-time users, who do not have an account on the computer, temporarily sign in to the local server or client computer with limited user rights. By default, the Guest account has a blank password. Because the Guest account can provide anonymous access, it is a security risk. For this reason, it is a best practice to leave the Guest account disabled, unless its use is entirely necessary.
Account group membership
By default, the Guest account is the only member of the default Guests group (SID S-1-5-32-546), which lets a user sign in to a server. On occasion, an administrator who is a member of the Administrators group can set up a user with a Guest account on one or more computers.
Security considerations
When enabling the Guest account, only grant limited rights and permissions. For security reasons, the Guest account should not be used over the network and made accessible to other computers.
In addition, the guest user in the Guest account should not be able to view the event logs. After the Guest account is enabled, it is a best practice to monitor the Guest account frequently to ensure that other users cannot use services and other resources, such as resources that were unintentionally left available by a previous user.
HelpAssistant account (installed with a Remote Assistance session)
The HelpAssistant account is a default local account that is enabled when a Remote Assistance session is run. This account is automatically disabled when no Remote Assistance requests are pending.
HelpAssistant is the primary account that is used to establish a Remote Assistance session. The Remote Assistance session is used to connect to another computer running the Windows operating system, and it is initiated by invitation. For solicited remote assistance, a user sends an invitation from their computer, through e-mail or as a file, to a person who can provide assistance. After the user’s invitation for a Remote Assistance session is accepted, the default HelpAssistant account is automatically created to give the person who provides assistance limited access to the computer. The HelpAssistant account is managed by the Remote Desktop Help Session Manager service.
DefaultAccount
The DefaultAccount, also known as the Default System Managed Account (DSMA), is a built-in account introduced in Windows 10 version 1607 and Windows Server 2016. The DSMA is a well-known user account type. It is a user neutral account that can be used to run processes that are either multi-user aware or user-agnostic. The DSMA is disabled by default on the desktop SKUs (full windows SKUs) and WS 2016 with the Desktop.
The DSMA has a well-known RID of 503. The security identifier (SID) of the DSMA will thus have a well-known SID in the following format: S-1-5-21-<ComputerIdentifier>-503
The DSMA is a member of the well-known group System Managed Accounts Group, which has a well-known SID of S-1-5-32-581.
The DSMA alias can be granted access to resources during offline staging even before the account itself has been created. The account and the group are created during first boot of the machine within the Security Accounts Manager (SAM).
How Windows uses the DefaultAccount
From a permission perspective, the DefaultAccount is a standard user account. The DefaultAccount is needed to run multi-user-manifested-apps (MUMA apps). MUMA apps run all the time and react to users signing in and signing out of the devices. Unlike Windows Desktop where apps run in context of the user and get terminated when the user signs off, MUMA apps run by using the DSMA.
MUMA apps are functional in shared session SKUs such as Xbox. For example, Xbox shell is a MUMA app. Today, Xbox automatically signs in as Guest account and all apps run in this context. All the apps are multi-user-aware and respond to events fired by user manager. The apps run as the Guest account.
Similarly, Phone auto logs in as a “DefApps” account which is akin to the standard user account in Windows but with a few extra privileges. Brokers, some services and apps run as this account.
In the converged user model, the multi-user-aware apps and multi-user-aware brokers will need to run in a context different from that of the users. For this purpose, the system creates DSMA.
How the DefaultAccount gets created on domain controllers
If the domain was created with domain controllers that run Windows Server 2016, the DefaultAccount will exist on all domain controllers in the domain. If the domain was created with domain controllers that run an earlier version of Windows Server, the DefaultAccount will be created after the PDC Emulator role is transferred to a domain controller that runs Windows Server 2016. The DefaultAccount will then be replicated to all other domain controllers in the domain.
Recommendations for managing the Default Account (DSMA)
Microsoft does not recommend changing the default configuration, where the account is disabled. There is no security risk with having the account in the disabled state. Changing the default configuration could hinder future scenarios that rely on this account.
Default local system accounts
SYSTEM
The SYSTEM account is used by the operating system and by services that run under Windows. There are many services and processes in the Windows operating system that need the capability to sign in internally, such as during a Windows installation. The SYSTEM account was designed for that purpose, and Windows manages the SYSTEM account’s user rights. It is an internal account that does not show up in User Manager, and it cannot be added to any groups.
On the other hand, the SYSTEM account does appear on an NTFS file system volume in File Manager in the Permissions portion of the Security menu. By default, the SYSTEM account is granted Full Control permissions to all files on an NTFS volume. Here the SYSTEM account has the same functional rights and permissions as the Administrator account.
Note To grant the account Administrators group file permissions does not implicitly give permission to the SYSTEM account. The SYSTEM account’s permissions can be removed from a file, but we do not recommend removing them.
NETWORK SERVICE
The NETWORK SERVICE account is a predefined local account used by the service control manager (SCM). A service that runs in the context of the NETWORK SERVICE account presents the computer’s credentials to remote servers.
Service Control Manager (SCM)
https://en.wikipedia.org/wiki/Service_Control_Manager
Service Control Manager (SCM) is a special system process under the Windows NT family of operating systems, which starts, stops and interacts with Windows service processes.
SCM is similar to init systems in Unix, Linux, FreeBSD and MacOS systems like System-V-Init, BSD-Init, Systemd, launchd in MacOS, and more. SCM uses the registry to determine and load services during startup, Systemd in contrast is a complete service management suite.
Introduction on Windows Services
https://www.installsetupconfig.com/win32programming/windowsservicesapis5_1.html
This account is not recognized by the security subsystem, so you cannot specify its name in a call to the LookupAccountName function. It has minimum privileges on the local computer and acts as the computer on the network.
This account can be specified in a call to the CreateService and ChangeServiceConfig functions. Note that this account does not have a password, so any password information that you provide in this call is ignored. While the security subsystem localizes this account name, the SCM does not support localized names. Therefore, you will receive a localized name for this account from the LookupAccountSid function, but the name of the account must be NT AUTHORITY\NetworkService when you call CreateService or ChangeServiceConfig, regardless of the locale, or unexpected results can occur.
A service that runs in the context of the NetworkService account presents the computer’s credentials to remote servers. By default, the remote token contains SIDs for the Everyone and Authenticated Users groups. The user SID is created from the SECURITY_NETWORK_SERVICE_RID value.
The NetworkService account has its own subkey under the HKEY_USERS registry key. Therefore, the HKEY_CURRENT_USER registry key is associated with the NetworkService account.
The NetworkService account has the following privileges:
- SE_ASSIGNPRIMARYTOKEN_NAME (disabled)
- SE_AUDIT_NAME (disabled)
- SE_CHANGE_NOTIFY_NAME (enabled)
- SE_CREATE_GLOBAL_NAME (enabled)
- SE_IMPERSONATE_NAME (enabled)
- SE_INCREASE_QUOTA_NAME (disabled)
- SE_SHUTDOWN_NAME (disabled)
- SE_UNDOCK_NAME (disabled)
- Any privileges assigned to users and authenticated users
For more information, see Service Security and Access Rights.
LOCAL SERVICE
The LOCAL SERVICE account is a predefined local account used by the service control manager. It has minimum privileges on the local computer and presents anonymous credentials on the network. For more information, see LocalService Account.
Enforce local account restrictions for remote access
The User Account Control (UAC) is a security feature in Windows that has been in use in Windows Server 2008 and in Windows Vista, and the operating systems to which the Applies To list refers. UAC enables you to stay in control of your computer by informing you when a program makes a change that requires administrator-level permission. UAC works by adjusting the permission level of your user account. By default, UAC is set to notify you when applications try to make changes to your computer, but you can change how often UAC notifies you.
UAC makes it possible for an account with administrative rights to be treated as a standard user non-administrator account until full rights, also called elevation, is requested and approved. For example, UAC lets an administrator enter credentials during a non-administrator’s user session to perform occasional administrative tasks without having to switch users, sign out, or use the Run as command.
In addition, UAC can require administrators to specifically approve applications that make system-wide changes before those applications are granted permission to run, even in the administrator’s user session.
For example, a default feature of UAC is shown when a local account signs in from a remote computer by using Network logon (for example, by using NET.EXE USE). In this instance, it is issued a standard user token with no administrative rights, but without the ability to request or receive elevation. Consequently, local accounts that sign in by using Network logon cannot access administrative shares such as C$, or ADMIN$, or perform any remote administration.
For more information about UAC, see User Account Control.
WDAGUtilityAccount local account
This account is part of Windows Defender Application Guard beginning with Windows 10 version 1709 (Fall Creators Update). This account remains disabled until Application Guard is enabled on your device. This item is integrated to the OS and is not considered as a threat/virus/malware.
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