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 e…
MITRE mitigation sourceAdversaryGraph public intelligence page
This page is part of Threat Matrix, the public browser workspace for the main AdversaryGraph platform. Use it for ATT&CK pivots, actor and technique context, similarity leads, detection coverage review, and analyst-ready investigation paths.
Validation disclaimer: TTP overlap, actor similarity, generated summaries, and coverage findings are investigation leads, not attribution proof or operational validation without analyst review.
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Hidden Users
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. 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. 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. 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). Display Managers are not anchored to specific distributions and may be changed by a user or adversary.
Open detection, hunting, mitigation, and evidence workspace
Detection logic
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. 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.
Observed actors
Correlated CTI and IR reports
Cyber Knowledge context
Use these routes to move from the ATT&CK behavior into explanation, implementation, evidence handling, validation, and defensive operations. Relevance is generated from explicit identifiers/names and governed topic mappings; it is not attribution evidence.
Malware Analysis & Reverse Engineering · Tactic learning route · 24/100Module 4 — Detection engineering and detection as code
Blue Team & Defensive Security · Tactic learning route · 24/100Disk, file-system, and persistence forensics
Digital Forensics & Incident Response (DFIR) · Tactic learning route · 24/100
MITRE mitigations
MITRE detection strategies and analytics
- AN1001 · Analytic 1001 — Registry modifications to HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\UserList setting user visibility to 0, or creation of user accounts not shown on login screen. Defender view: correlation of account creation with registry edits that mark users hidden.
- AN1002 · Analytic 1002 — Use of gsettings or direct Display Manager modifications to hide users from greeter login screen. Defender view: anomalous command execution modifying org.gnome.login-screen or other greeter configurations.
- AN1003 · Analytic 1003 — User creation or modification via dscl with IsHidden=1, UID<500, or plist edits to com.apple.loginwindow Hide500Users flag. Defender view: correlation of hidden account attributes with login screen exclusion.