Android Accessibility Pentest

Android Accessibility Service Pentesting

A skill for analyzing, detecting, and testing Android Accessibility Service abuse patterns in security assessments.

When to use this skill

Use this skill when:

• Analyzing Android apps for malicious accessibility services
• Testing for overlay phishing or credential harvesting vulnerabilities
• Investigating RATs like ClayRat, PlayPraetor, SpyNote, BrasDex, SOVA, ToxicPanda
• Assessing banking app security against accessibility-based attacks
• Detecting on-device fraud (ODF) automation patterns
• Reviewing APK manifests for suspicious accessibility configurations
• Hardening apps against accessibility service abuse
• Understanding Android RAT command & control workflows

Core Concepts

What is AccessibilityService Abuse?

AccessibilityService was designed to help users with disabilities interact with Android devices. However, the same powerful automation APIs can be weaponized by malware to gain complete remote control of the handset without root privileges.

Key capabilities attackers exploit:

• Capture every UI event and text on screen
• Inject synthetic gestures (dispatchGesture)
• Perform global actions (performGlobalAction)
• Draw full-screen overlays using TYPE_ACCESSIBILITY_OVERLAY (no SYSTEM_ALERT_WINDOW prompt!)
• Silently grant additional runtime permissions by clicking system dialogs

The Attack Recipe

1. Social engineering → Victim enables rogue accessibility service (requires explicit user action for BIND_ACCESSIBILITY_SERVICE permission)
2. Leverage the service → Capture UI events, inject gestures, draw overlays, auto-grant permissions
3. Exfiltrate or perform ODF → Real-time fraud while user sees a normal screen

Detection Methods

1. Check Enabled Accessibility Services

# List all enabled accessibility services
adb shell settings get secure enabled_accessibility_services

# Detailed accessibility dump
adb shell dumpsys accessibility | grep "Accessibility Service"

# Check for suspicious services in Settings
# Settings → Accessibility → Downloaded services
# Look for apps NOT from Google Play

2. Analyze APK Manifest

Look for these patterns in AndroidManifest.xml:

<!-- Suspicious accessibility service declaration -->
<service
    android:name="com.evil.rat.EvilService"
    android:permission="android.permission.BIND_ACCESSIBILITY_SERVICE"
    android:exported="false">
    
    <intent-filter>
        <action android:name="android.accessibilityservice.AccessibilityService" />
    </intent-filter>
    
    <meta-data android:name="android.accessibilityservice"
        android:resource="@xml/evil_accessibility_config"/>
</service>

Red flags in accessibility config XML:

• android:canPerformGestures="true" - Can inject gestures
• android:canRetrieveWindowContent="true" - Can read screen content
• android:accessibilityEventTypes="typeAllMask" - Captures all events
• android:notificationTimeout="200" - Very low timeout (aggressive monitoring)

3. Runtime Detection

# Check running services
adb shell dumpsys activity services | grep -i accessibility

# Check for overlay windows
adb shell dumpsys window windows | grep -i overlay

# Check device admin receivers
adb shell dumpsys device_policy

Abuse Patterns to Detect

Pattern 1: Overlay Phishing (Credential Harvesting)

What it does: Transparent/opaque WebView added via TYPE_ACCESSIBILITY_OVERLAY to capture credentials while real app receives gestures.

Detection indicators:

• WindowManager.LayoutParams with TYPE_ACCESSIBILITY_OVERLAY
• FLAG_NOT_FOCUSABLE | FLAG_NOT_TOUCH_MODAL flags
• WebView or custom view added to WindowManager
• No SYSTEM_ALERT_WINDOW permission requested

ClayRat commands:

• show_block_screen / hide_block_screen - Toggle overlay templates
• Downloads overlay templates from C2
• Can black out screen, show fake system updates, or display interactive PIN pad

Pattern 2: On-Device Fraud Automation

What it does: Real-time unauthorized transactions via WebSocket commands translated to low-level gestures.

Detection indicators:

• Persistent WebSocket connection (often port 8282)
• Commands like init, update, alert_arr, report_list
• Banking app navigation patterns in logs
• dispatchGesture calls with banking app coordinates

Malware families: PlayPraetor, ClayRat

Pattern 3: Screen Streaming & Monitoring

What it does: VNC-like remote desktop via MediaProjection + Accessibility auto-click.

Detection indicators:

• MediaProjection token creation
• VirtualDisplay with ImageReader
• Foreground service for frame capture
• JPEG/PNG encoding with quality parameter
• HTTP→WebSocket upgrade with custom user-agent (e.g., ClayRemoteDesktop)

ClayRat commands:

• turbo_screen - Triggers MediaProjection consent (auto-clicked)
• start_desktop / stop_desktop - Manage capture threads
• screen_tap, screen_swipe, input_text - Replay gestures
• set_quality - Adjust encoding quality (default 60)

Pattern 4: Lock-Screen Credential Theft

What it does: Captures PIN, password, or pattern from lock screen and enables auto-unlock.

Detection indicators:

• Subscribes to TYPE_WINDOW_CONTENT_CHANGED / TYPE_VIEW_TEXT_CHANGED
• Listens to com.android.systemui (Keyguard) events
• Stores credentials in SharedPreferences under lock_password_storage
• auto_unlock command triggers unlock_device / screen_on

Capture methods:

• PIN: Watches keypad button presses
• Password: Concatenates strings from focused password field
• Pattern: Records ordered node indices from gesture coordinates

Pattern 5: Notification Phishing & Harvesting

What it does: Notification Listener dumps OTP/MFA messages and crafts fake notifications.

Detection indicators:

• NotificationListenerService registered
• get_push_notifications command dumps visible notifications
• notifications_enabled flag for real-time streaming
• send_push_notification crafts fake interactive notifications

Pattern 6: Telephony & SMS Command Channel

What it does: Complete modem control after setting RAT as default SMS app.

Detection indicators:

• Default SMS app permission granted
• Commands: send_sms, retransmishion, messsms, make_call
• get_sms_list, get_sms, get_call_log, get_calls
• Contacts database iteration for worm-like propagation

Pattern 7: Discovery, Collection & Proxying

What it does: Environment mapping and C2 resilience.

Detection indicators:

• get_apps / get_apps_list - Enumerate installed packages (ATT&CK T1418)
• get_device_info - Model, OS version, battery state (T1426)
• get_cam / get_camera - Front-camera stills
• get_keylogger_data - Lock PINs, passwords, view descriptions
• get_proxy_data - Proxy WebSocket URL for HTTP/HTTPS tunneling (T1481.002 / T1646)

Packed Accessibility Droppers

ClayRat v3.0.8 pattern (ATT&CK T1406.002):

1. Streams encrypted blob from assets/*.dat
2. Decrypts with hard-coded AES/CBC key + IV
3. Writes plaintext DEX to app's private dir
4. Loads via DexClassLoader (spyware classes only in memory)

Detection:

• Look for assets/*.dat or similar encrypted blobs
• Search for AES/CBC decryption patterns in decompiled code
• DexClassLoader instantiation with temp DEX files
• getCodeCacheDir() usage for loading

C2 Workflow Analysis

PlayPraetor Command & Control

1. HTTP(S) heartbeat - Iterate hard-coded domains until one answers POST /app/searchPackageName
2. WebSocket (port 8282) - Bidirectional JSON commands:
   • update - Push new config/APKs
   • alert_arr - Configure overlay templates
   • report_list - Send targeted package names
   • heartbeat_web - Keep-alive
3. RTMP (port 1935) - Live screen/video streaming
4. REST exfiltration:
   • /app/saveDevice - Fingerprint
   • /app/saveContacts | /app/saveSms | /app/uploadImageBase64
   • /app/saveCardPwd - Bank credentials

Hardening Recommendations

For App Developers

1. Mark sensitive views:

   android:accessibilityDataSensitive="accessibilityDataPrivateYes"
   

   (API 34+)

2. Prevent tap/overlay hijacking:

   setFilterTouchesWhenObscured(true);
   window.setFlags(FLAG_SECURE, FLAG_SECURE);
   

3. Detect overlays:

   // Poll display flags
   WindowManager.getDefaultDisplay().getFlags();
   // Or use ViewRootImpl API
   

4. Refuse operation when suspicious:

   if (Settings.canDrawOverlays() || hasUntrustedAccessibilityService()) {
       // Block sensitive operations
   }
   

For Enterprise/MDM

• Enforce ACCESSIBILITY_ENFORCEMENT_DEFAULT_DENY (Android 13+) to block sideloaded services
• Monitor enabled_accessibility_services setting changes
• Alert on non-Play Store accessibility services

Testing Checklist

When assessing an app for accessibility abuse:

• Check manifest for BIND_ACCESSIBILITY_SERVICE permission
• Review accessibility config XML for dangerous flags
• Test if app operates when suspicious accessibility service is enabled
• Check for overlay detection mechanisms
• Verify sensitive data is marked accessibilityDataSensitive
• Test with FLAG_SECURE enabled
• Monitor for dispatchGesture and performGlobalAction calls
• Check for MediaProjection abuse patterns
• Review network traffic for C2 patterns (WebSocket 8282, RTMP 1935)
• Analyze assets for encrypted payloads

References

• Return of ClayRat: Expanded Features and Techniques
• ClayRat v3 IoCs (Zimperium)
• PlayPraetor's evolving threat
• Android accessibility documentation
• The Rise of RatOn: From NFC heists to remote control
• GhostTap/NFSkate – NFC relay cash-out tactic