Access Token Manipulation: Token Impersonation/Theft
Adversaries may duplicate then impersonate another user's token to escalate privileges and bypass access controls. An adversary can create a new access token that duplicates an existing token using
DuplicateToken(Ex). 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 do this when they have a specific, existing process they want to assign the new token to. For example, this may be useful for when the target user has a non-network logon session on the system.
|Privileged Account Management||
Limit permissions so that users and user groups cannot create tokens. This setting should be defined for the local system account only. GPO: Computer Configuration > [Policies] > Windows Settings > Security Settings > Local Policies > User Rights Assignment: Create a token object.  Also define who can create a process level token to only the local and network service through GPO: Computer Configuration > [Policies] > Windows Settings > Security Settings > Local Policies > User Rights Assignment: Replace a process level token.
Administrators should log in as a standard user but run their tools with administrator privileges using the built-in access token manipulation command
|User Account Management||
An adversary must already have administrator level access on the local system to make full use of this technique; be sure to restrict users and accounts to the least privileges they require.
If an adversary is using a standard command-line shell, analysts can detect token manipulation by auditing command-line activity. Specifically, analysts should look for use of the
runas command. Detailed command-line logging is not enabled by default in Windows.
Analysts can also monitor for use of Windows APIs such as
ImpersonateLoggedOnUser , and
SetThreadToken and correlate activity with other suspicious behavior to reduce false positives that may be due to normal benign use by users and administrators.
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