System Owner/User Discovery

What the technique is

Adversaries may attempt to identify the primary user, currently logged in user, set of users that commonly uses a system, or whether a user is actively using the system. They may do this, for example, by retrieving account usernames or by using OS Credential Dumping. The information may be collected in a number of different ways using other Discovery techniques, because user and username details are prevalent throughout a system and include running process ownership, file/directory ownership, session information, and system logs. Adversaries may use the information from System Owner/User Discovery during automated discovery to shape follow-on behaviors, including whether or not the adversary fully infects the target and/or attempts specific actions. Various utilities and commands may acquire this information, including whoami. In macOS and Linux, the currently logged in user can be identified with w and who. On macOS the dscl. list /Users | grep -v '_' command can also be used to enumerate user accounts. Environment variables, such as %USERNAME% and $USER, may also be used to access this information. On network devices, Network Device CLI commands such as show users and show ssh can be used to display users currently logged into the device.

What MITRE says you would watch

• AN0254

  Adversary launches built-in system tools (e.g., whoami, query user, net user) or scripts that enumerate user account information via local execution or remote API queries (e.g., WMI, PowerShell).

• AN0255

  Adversary runs commands like whoami, id, w, or cat /etc/passwd from non-interactive or scripting contexts to enumerate system user details.

• AN0256

  Adversary uses dscl, who, or environment variables like $USER to identify accounts or sessions via Terminal or malicious LaunchAgents.