System Owner/User Discovery

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 <code>whoami</code>. In macOS and Linux, the currently logged in user can be identified with <code>w</code> and <code>who</code>. On macOS the <code>dscl . list /Users | grep -v '_'</code> command can also be used to enumerate user accounts. Environment variables, such as <code>%USERNAME%</code> and <code>$USER</code>, 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.¹²

1. show_ssh_users_cmd_cisco
2. US-CERT TA18-106A Network Infrastructure Devices 2018

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Auto-ingested and not human-reviewed; confidence and validity read by citation.