Adversaries may modify access tokens to operate under a different user or system security context to perform actions and bypass access controls. Windows uses access tokens to determine the ownership of a running process. A user can manipulate access tokens to make a running process appear as though it is the child of a different process or belongs to someone other than the user that started the process. When this occurs, the process also takes on the security context associated with the new token.

An adversary can use built-in Windows API functions to copy access tokens from existing processes; this is known as token stealing. These token can then be applied to an existing process (i.e. [Token Impersonation/Theft](https://attack.mitre.org/techniques/T1134/001)) or used to spawn a new process (i.e. [Create Process with Token](https://attack.mitre.org/techniques/T1134/002)). An adversary must already be in a privileged user context (i.e. administrator) to steal a token. However, adversaries commonly use token stealing to elevate their security context from the administrator level to the SYSTEM level. An adversary can then use a token to authenticate to a remote system as the account for that token if the account has appropriate permissions on the remote system.(Citation: Pentestlab Token Manipulation)

Any standard user can use the <code>runas</code> command, and the Windows API functions, to create impersonation tokens; it does not require access to an administrator account. There are also other mechanisms, such as Active Directory fields, that can be used to modify access tokens.
Access Token Manipulation
source_name: mitre-attack  url: https://attack.mitre.org/techniques/T1134  external_id: T1134     source_name: BlackHat Atkinson Winchester Token Manipulation  description: Atkinson, J., Winchester, R. (2017, December 7). A Process is No One: Hunting for Token Manipulation. Retrieved December 21, 2017.  url: https://www.blackhat.com/docs/eu-17/materials/eu-17-Atkinson-A-Process-Is-No-One-Hunting-For-Token-Manipulation.pdf     source_name: Microsoft Command-line Logging  description: Mathers, B. (2017, March 7). Command line process auditing. Retrieved April 21, 2017.  url: https://technet.microsoft.com/en-us/windows-server-docs/identity/ad-ds/manage/component-updates/command-line-process-auditing     source_name: Microsoft LogonUser  description: Microsoft TechNet. (n.d.). Retrieved April 25, 2017.  url: https://msdn.microsoft.com/en-us/library/windows/desktop/aa378184(v=vs.85).aspx     source_name: Microsoft DuplicateTokenEx  description: Microsoft TechNet. (n.d.). Retrieved April 25, 2017.  url: https://msdn.microsoft.com/en-us/library/windows/desktop/aa446617(v=vs.85).aspx     source_name: Microsoft ImpersonateLoggedOnUser  description: Microsoft TechNet. (n.d.). Retrieved April 25, 2017.  url: https://msdn.microsoft.com/en-us/library/windows/desktop/aa378612(v=vs.85).aspx     source_name: Pentestlab Token Manipulation  description: netbiosX. (2017, April 3). Token Manipulation. Retrieved April 21, 2017.  url: https://pentestlab.blog/2017/04/03/token-manipulation/     