Hide Artifacts: Скрытые пользователи
Other sub-techniques of Hide Artifacts (14)
Adversaries may use hidden users to hide the presence of user accounts they create or modify. Administrators may want to hide users when there are many user accounts on a given system or if they want to hide their administrative or other management accounts from other users.
In macOS, adversaries can create or modify a user to be hidden through manipulating plist files, folder attributes, and user attributes. To prevent a user from being shown on the login screen and in System Preferences, adversaries can set the userID to be under 500 and set the key value Hide500Users to TRUE in the /Library/Preferences/com.apple.loginwindow plist file.(Citation: Cybereason OSX Pirrit) Every user has a userID associated with it. When the Hide500Users key value is set to TRUE, users with a userID under 500 do not appear on the login screen and in System Preferences. Using the command line, adversaries can use the dscl utility to create hidden user accounts by setting the IsHidden attribute to 1. Adversaries can also hide a user’s home folder by changing the chflags to hidden.(Citation: Apple Support Hide a User Account)
Adversaries may similarly hide user accounts in Windows. Adversaries can set the HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\UserList Registry key value to 0 for a specific user to prevent that user from being listed on the logon screen.(Citation: FireEye SMOKEDHAM June 2021)(Citation: US-CERT TA18-074A)
On Linux systems, adversaries may hide user accounts from the login screen, also referred to as the greeter. The method an adversary may use depends on which Display Manager the distribution is currently using. For example, on an Ubuntu system using the GNOME Display Manger (GDM), accounts may be hidden from the greeter using the gsettings command (ex: sudo -u gdm gsettings set org.gnome.login-screen disable-user-list true).(Citation: Hide GDM User Accounts) Display Managers are not anchored to specific distributions and may be changed by a user or adversary.
Примеры процедур |
|
| Название | Описание |
|---|---|
| Dragonfly |
Dragonfly has modified the Registry to hide created user accounts.(Citation: US-CERT TA18-074A) |
| SMOKEDHAM |
SMOKEDHAM has modified the Registry to hide created user accounts from the Windows logon screen. (Citation: FireEye SMOKEDHAM June 2021) |
| Kimsuky |
Kimsuky has run |
Контрмеры |
|
| Контрмера | Описание |
|---|---|
| Operating System Configuration |
Operating System Configuration involves adjusting system settings and hardening the default configurations of an operating system (OS) to mitigate adversary exploitation and prevent abuse of system functionality. Proper OS configurations address security vulnerabilities, limit attack surfaces, and ensure robust defense against a wide range of techniques. This mitigation can be implemented through the following measures: Disable Unused Features: - Turn off SMBv1, LLMNR, and NetBIOS where not needed. - Disable remote registry and unnecessary services. Enforce OS-level Protections: - Enable Data Execution Prevention (DEP), Address Space Layout Randomization (ASLR), and Control Flow Guard (CFG) on Windows. - Use AppArmor or SELinux on Linux for mandatory access controls. Secure Access Settings: - Enable User Account Control (UAC) for Windows. - Restrict root/sudo access on Linux/macOS and enforce strong permissions using sudoers files. File System Hardening: - Implement least-privilege access for critical files and system directories. - Audit permissions regularly using tools like icacls (Windows) or getfacl/chmod (Linux/macOS). Secure Remote Access: - Restrict RDP, SSH, and VNC to authorized IPs using firewall rules. - Enable NLA for RDP and enforce strong password/lockout policies. Harden Boot Configurations: - Enable Secure Boot and enforce UEFI/BIOS password protection. - Use BitLocker or LUKS to encrypt boot drives. Regular Audits: - Periodically audit OS configurations using tools like CIS Benchmarks or SCAP tools. *Tools for Implementation* Windows: - Microsoft Group Policy Objects (GPO): Centrally enforce OS security settings. - Windows Defender Exploit Guard: Built-in OS protection against exploits. - CIS-CAT Pro: Audit Windows security configurations based on CIS Benchmarks. Linux/macOS: - AppArmor/SELinux: Enforce mandatory access controls. - Lynis: Perform comprehensive security audits. - SCAP Security Guide: Automate configuration hardening using Security Content Automation Protocol. Cross-Platform: - Ansible or Chef/Puppet: Automate configuration hardening at scale. - OpenSCAP: Perform compliance and configuration checks. |
Обнаружение
Monitor for users that may be hidden from the login screen but still present in additional artifacts of usage such as directories and authentication logs.
Monitor processes and command-line events for actions that could be taken to add a new user and subsequently hide it from login screens. Monitor Registry events for modifications to the HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\UserList key.
In macOS, monitor for commands, processes, and file activity in combination with a user that has a userID under 500.(Citation: Cybereason OSX Pirrit) Monitor for modifications to set the Hide500Users key value to TRUE in the /Library/Preferences/com.apple.loginwindow plist file. Monitor the command line for usage of the dscl . create command with the IsHidden attribute set to 1.(Citation: Apple Support Hide a User Account)
Ссылки
- US-CERT. (2018, March 16). Alert (TA18-074A): Russian Government Cyber Activity Targeting Energy and Other Critical Infrastructure Sectors. Retrieved June 6, 2018.
- Ji Mingkui. (2021, June 17). How to Hide All The User Accounts in Ubuntu 20.04, 21.04 Login Screen. Retrieved March 15, 2022.
- FireEye. (2021, June 16). Smoking Out a DARKSIDE Affiliate’s Supply Chain Software Compromise. Retrieved September 22, 2021.
- Apple. (2020, November 30). Hide a user account in macOS. Retrieved December 10, 2021.
- Amit Serper. (2016). Cybereason Lab Analysis OSX.Pirrit. Retrieved December 10, 2021.
- KISA. (2021). Phishing Target Reconnaissance and Attack Resource Analysis Operation Muzabi. Retrieved March 8, 2024.
Связанные риски
Каталоги
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