Event 4696: A primary token was assigned to process.

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.

Adversaries may duplicate then impersonate another user's existing token to escalate privileges and bypass access controls. For example, an adversary can duplicate an existing token using `DuplicateToken` or `DuplicateTokenEx`.(Citation: DuplicateToken function) The token can then be used with `ImpersonateLoggedOnUser` to allow the calling thread to impersonate a logged on user's security context, or with `SetThreadToken` to assign the impersonated token to a thread. An adversary may perform [Token Impersonation/Theft](https://attack.mitre.org/techniques/T1134/001) when they have a specific, existing process they want to assign the duplicated token to. For example, this may be useful for when the target user has a non-network logon session on the system. When an adversary would instead use a duplicated token to create a new process rather than attaching to an existing process, they can additionally [Create Process with Token](https://attack.mitre.org/techniques/T1134/002) using `CreateProcessWithTokenW` or `CreateProcessAsUserW`. [Token Impersonation/Theft](https://attack.mitre.org/techniques/T1134/001) is also distinct from [Make and Impersonate Token](https://attack.mitre.org/techniques/T1134/003) in that it refers to duplicating an existing token, rather than creating a new one.

Adversaries may create a new process with an existing token to escalate privileges and bypass access controls. Processes can be created with the token and resulting security context of another user using features such as <code>CreateProcessWithTokenW</code> and <code>runas</code>.(Citation: Microsoft RunAs) Creating processes with a token not associated with the current user may require the credentials of the target user, specific privileges to impersonate that user, or access to the token to be used. For example, the token could be duplicated via [Token Impersonation/Theft](https://attack.mitre.org/techniques/T1134/001) or created via [Make and Impersonate Token](https://attack.mitre.org/techniques/T1134/003) before being used to create a process. While this technique is distinct from [Token Impersonation/Theft](https://attack.mitre.org/techniques/T1134/001), the techniques can be used in conjunction where a token is duplicated and then used to create a new process.