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Input Injection

A malicious application can inject input to the user interface to mimic user interaction through the abuse of Android's accessibility APIs.

Input Injection can be achieved using any of the following methods:

  • Mimicking user clicks on the screen, for example to steal money from a user's PayPal account.[1]
  • Injecting global actions, such as GLOBAL_ACTION_BACK (programatically mimicking a physical back button press), to trigger actions on behalf of the user.[2]
  • Inserting input into text fields on behalf of the user. This method is used legitimately to auto-fill text fields by applications such as password managers.[3]
ID: T1516
Tactic Type: Post-Adversary Device Access
Tactic: Defense Evasion, Impact
Platform: Android
Contributors: Lukáš Štefanko, ESET
Version: 1.0
Created: 15 September 2019
Last Modified: 24 September 2019

Procedure Examples

Name Description
Gustuff

Gustuff injects the global action GLOBAL_ACTION_BACK to mimic pressing the back button to close the application if a call to an open antivirus application is detected.[2]

Riltok

Riltok injects input to set itself as the default SMS handler by clicking the appropriate places on the screen. It can also close or minimize targeted antivirus applications and the device security settings screen.[4]

Mitigations

Mitigation Description
Application Vetting

Applications that register an accessibility service should be scrutinized further for malicious behavior.

Enterprise Policy

An EMM/MDM can use the Android DevicePolicyManager.setPermittedAccessibilityServices method to whitelist applications that are allowed to use Android's accessibility features.

User Guidance

Users should be warned against granting access to accessibility features, and to carefully scrutinize applications that request this dangerous permission.

Detection

Users can view applications that have registered accessibility services in the accessibility menu within the device settings.

References