Accessibility Features
Accessibility Features [T1546.008]
Information
Name: Accessibility Features
ID: T1546.008
Technique: T1546
Introduction
Accessibility Features (T1546.008) is a sub-technique of the MITRE ATT&CK framework under Persistence (T1546). Adversaries leverage built-in accessibility tools and features provided by operating systems to maintain persistent access within compromised environments. Accessibility features, designed to assist users with disabilities, can be abused by attackers to execute malicious payloads automatically, typically during system startup or user login processes. Exploiting these legitimate functionalities allows adversaries to evade suspicion and maintain prolonged access.
Deep Dive Into Technique
Accessibility features are native operating system capabilities intended to aid users with disabilities, such as screen magnifiers, on-screen keyboards, text-to-speech engines, and sticky keys. Attackers abuse these features by replacing or manipulating the legitimate executables or registry keys associated with them, effectively causing malicious payloads to execute automatically at specific trigger events like system reboot, user login, or when certain accessibility shortcuts are activated.
Technical details and execution methods include:
Sticky Keys (Windows):
Attackers commonly exploit Sticky Keys by replacing the executable (
sethc.exe) with a malicious binary or a command prompt (cmd.exe).Pressing the Shift key five times triggers the malicious executable, providing attackers with elevated privileges or persistent access.
Utilman.exe Replacement (Windows):
Attackers replace the Utility Manager executable (
utilman.exe) with malicious binaries.Triggered by pressing Windows Key + U at the login screen, this technique allows attackers to bypass authentication mechanisms and gain unauthorized access to the system.
Narrator and Magnifier Abuse (Windows):
Attackers modify or replace executables associated with Narrator (
Narrator.exe) and Magnifier (Magnify.exe) accessibility features.These executables can be triggered via keyboard shortcuts or automatically upon system startup, enabling persistent execution of malicious payloads.
Registry Manipulation (Windows):
Attackers modify registry keys under
HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Optionsto redirect accessibility feature executables to malicious binaries.This technique ensures persistence and stealthy execution of attacker-controlled payloads.
When this Technique is Usually Used
Adversaries typically employ Accessibility Features (T1546.008) sub-technique during the following attack scenarios and stages:
Persistence Stage:
Attackers establish persistent footholds within compromised systems by ensuring malicious payloads execute automatically upon startup or user login.
Privilege Escalation and Credential Access:
Exploiting accessibility features often provides attackers with interactive shells or system-level access at login screens, facilitating credential theft or privilege escalation.
Lateral Movement and Post-Exploitation:
Attackers frequently use this technique after initial compromise to maintain stealthy access, enabling further lateral movement and deeper infiltration into victim networks.
Physical Access Scenarios:
Attackers with physical access to systems (e.g., insider threats or malicious actors with temporary access) commonly exploit accessibility features to bypass authentication and gain persistent administrative access.
How this Technique is Usually Detected
Detection of malicious use of Accessibility Features involves multiple methods, tools, and indicators of compromise (IoCs):
Monitoring File System Changes:
Track unauthorized modifications or replacements of accessibility executables (
sethc.exe,utilman.exe,Narrator.exe,Magnify.exe) located inC:\Windows\System32\.
Registry Auditing and Monitoring:
Monitor registry keys under
HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Optionsfor suspicious modifications or redirections to unexpected binaries.
Event Log Analysis:
Analyze Windows Event Logs for unusual executions or attempts to trigger accessibility features at login screens or during system startup.
Integrity Checking Tools:
Employ file integrity monitoring (FIM) solutions and endpoint detection and response (EDR) tools to detect unauthorized file replacements or modifications.
Behavioral Analysis and Endpoint Detection Solutions:
Endpoint security tools with behavioral detection capabilities identify anomalous behaviors associated with accessibility feature abuse, such as unexpected process executions, privilege escalations, or suspicious command shells.
Indicators of Compromise (IoCs) include:
Unexpected modification timestamps on accessibility executables.
Presence of unauthorized binaries or renamed system executables in system directories.
Suspicious registry entries redirecting legitimate accessibility features to malicious executables.
Unusual execution patterns of accessibility processes during login or startup.
Why it is Important to Detect This Technique
Early detection of Accessibility Features abuse is critical due to the significant impacts and risks posed to compromised systems and networks:
Persistent Unauthorized Access:
Attackers leverage accessibility feature abuse to gain persistent footholds, enabling prolonged access and further exploitation.
Privilege Escalation and Credential Theft:
Abuse of accessibility features often grants attackers elevated privileges or direct access to sensitive credentials, increasing the severity of compromise.
Stealth and Evasion:
Exploiting legitimate OS functionalities enables attackers to evade traditional detection mechanisms, making early detection crucial to prevent prolonged, undetected intrusions.
Risk of Data Exfiltration and System Damage:
Persistent attacker access increases the risk of sensitive data theft, sabotage, ransomware deployment, and other destructive activities.
Compliance and Regulatory Risks:
Undetected persistent threats leveraging accessibility features can lead to regulatory non-compliance, data breaches, and significant financial or reputational damages.
Examples
Real-world examples illustrating Accessibility Features abuse include:
Sticky Keys Exploitation:
Attack Scenario:
Attacker gains initial physical or remote access to a Windows system.
Replaces
sethc.exewithcmd.exe.Presses Shift key five times at login screen, spawning an administrative command prompt without authentication.
Tools Used:
Built-in Windows command prompt (
cmd.exe), standard Windows utilities.
Impact:
Unauthorized administrative access, facilitating credential theft, privilege escalation, and persistent access.
Utilman.exe Replacement:
Attack Scenario:
Adversary replaces
utilman.exewith a malicious executable or command shell.Presses Windows Key + U at login screen to trigger malicious payload execution.
Tools Used:
Native Windows tools, custom malware payloads.
Impact:
Bypasses authentication, allowing direct administrative access and persistence.
Narrator and Magnifier Abuse:
Attack Scenario:
Attacker modifies registry entries or replaces binaries (
Narrator.exe,Magnify.exe) with malicious payloads.Payload executes automatically at system startup or triggered by accessibility keyboard shortcuts.
Tools Used:
Custom malware binaries, registry editors, scripting tools.
Impact:
Persistent execution of attacker-controlled payloads, enabling stealthy command-and-control, data exfiltration, and lateral movement.
APT Groups and Malware Families:
Advanced Persistent Threat (APT) groups, such as APT29, have historically leveraged accessibility feature abuses as part of their persistence and privilege escalation tactics.
Malware families like TrickBot and Ryuk ransomware have also demonstrated capabilities to exploit accessibility features for persistent access and lateral movement.
In each scenario, attackers exploit legitimate accessibility features to evade detection, maintain persistent access, escalate privileges, and facilitate further malicious activities, underscoring the importance of proactive detection and mitigation measures.
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