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Device Lockout

An adversary may seek to lock the legitimate user out of the device, for example to inhibit user interaction or to obtain a ransom payment.

On Android versions prior to 7, apps can abuse Device Administrator access to reset the device lock passcode to prevent the user from unlocking the device. After Android 7, only device or profile owners (e.g. MDMs) can reset the device’s passcode.[1]

On iOS devices, this technique does not work because mobile device management servers can only remove the screen lock passcode, they cannot set a new passcode. However, on jailbroken devices, malware has been discovered that can lock the user out of the device.[2]

ID: T1446
Tactic Type: Post-Adversary Device Access
Tactic: Impact, Defense Evasion
Platform: Android, iOS
MTC ID: APP-28
Version: 2.0
Created: 25 October 2017
Last Modified: 09 October 2019

Procedure Examples

Name Description
Charger

Charger locks the device if it is granted admin permissions, displaying a message demanding a ransom payment.[5]

KeyRaider

KeyRaider has built-in functionality to lock victims out of devices and hold them for ransom.[2]

Monokle

Monokle can reset the user's password/PIN.[6]

Rotexy

Rotexy can lock an HTML page in the foreground, requiring the user enter credit card information that matches information previously intercepted in SMS messages, such as the last 4 digits of a credit card number. If attempts to revoke administrator permissions are detected, Rotexy periodically switches off the phone screen to inhibit permission removal.[7]

Xbot

Xbot can remotely lock infected Android devices and ask for a ransom.[4]

Mitigations

Mitigation Description
Application Vetting

It is rare for applications to utilize Device Administrator access. App vetting can detect apps that do so, and those apps should be closely scrutinized. A static analysis approach can be used to identify ransomware apps including apps that abuse Device Administrator access.[3]

Caution with Device Administrator Access
Deploy Compromised Device Detection Method
Use Recent OS Version

Detection

On Android, users can review which applications have device administrator access in the device settings, and revoke permission where appropriate.

References