Call Control

Adversaries may make, forward, or block phone calls without user authorization. This could be used for adversary goals such as audio surveillance, blocking or forwarding calls from the device owner, or C2 communication.

Several permissions may be used to programmatically control phone calls, including:

  • ANSWER_PHONE_CALLS - Allows the application to answer incoming phone calls[1]
  • CALL_PHONE - Allows the application to initiate a phone call without going through the Dialer interface[1]
  • PROCESS_OUTGOING_CALLS - Allows the application to see the number being dialed during an outgoing call with the option to redirect the call to a different number or abort the call altogether[1]
  • MANAGE_OWN_CALLS - Allows a calling application which manages its own calls through the self-managed ConnectionService APIs[1]
  • BIND_TELECOM_CONNECTION_SERVICE - Required permission when using a ConnectionService[1]
  • WRITE_CALL_LOG - Allows an application to write to the device call log, potentially to hide malicious phone calls[1]

When granted some of these permissions, an application can make a phone call without opening the dialer first. However, if an application desires to simply redirect the user to the dialer with a phone number filled in, it can launch an Intent using Intent.ACTION_DIAL, which requires no specific permissions. This then requires the user to explicitly initiate the call or use some form of Input Injection to programmatically initiate it.

ID: T1616
Sub-techniques:  No sub-techniques
Tactic Type: Post-Adversary Device Access
Platforms: Android
Contributors: Gaetan van Diemen, ThreatFabric
Version: 1.2
Created: 20 September 2021
Last Modified: 10 August 2023

Procedure Examples

ID Name Description
S0292 AndroRAT

AndroRAT can make phone calls.[2]

S0422 Anubis

Anubis can make phone calls.[3]

S1094 BRATA

BRATA can hide incoming calls by setting ring volume to 0 and showing a blank screen overlay.[4]

S0655 BusyGasper

BusyGasper can open a hidden menu when a specific phone number is called from the infected device.[5]

S0529 CarbonSteal

CarbonSteal can silently accept an incoming phone call.[6]

S1054 Drinik

Drinik can use the Android CallScreeningService to silently block incoming calls.[7]

S1092 Escobar

Escobar can initiate phone calls.[8]

S1080 Fakecalls

Fakecalls can intercept and imitate phone conversations by breaking the connection and displaying a fake call screen. It can also make outgoing calls and spoof incoming calls.[9]

S0407 Monokle

Monokle can be controlled via phone call from a set of "control phones."[10]

S1069 TangleBot

TangleBot can make and block phone calls.[11]

Mitigations

ID Mitigation Description
M1011 User Guidance

Users should be encouraged to be very careful with what applications they grant phone call-based permissions to. Further, users should not change their default call handler to applications they do not recognize.

Detection

ID Data Source Data Component Detects
DS0042 User Interface System Notifications

The user can review available call logs for irregularities, such as missing or unrecognized calls.

System Settings

The user can view their default phone app in device settings.

References