Phishing: Spearphishing Voice

Adversaries may use voice communications to ultimately gain access to victim systems. Spearphishing voice is a specific variant of spearphishing. It is different from other forms of spearphishing in that it employs the use of manipulating a user into providing access to systems through a phone call or other forms of voice communications. Spearphishing frequently involves social engineering techniques, such as posing as a trusted source (ex: Impersonation) and/or creating a sense of urgency or alarm for the recipient.

All forms of phishing are electronically delivered social engineering. In this scenario, adversaries are not directly sending malware to a victim vice relying on User Execution for delivery and execution. For example, victims may receive phishing messages that instruct them to call a phone number where they are directed to visit a malicious URL, download malware,[1][2] or install adversary-accessible remote management tools (Remote Access Tools) onto their computer.[3]

Adversaries may also combine voice phishing with Multi-Factor Authentication Request Generation in order to trick users into divulging MFA credentials or accepting authentication prompts.[4]

ID: T1566.004
Sub-technique of:  T1566
Tactic: Initial Access
Platforms: Identity Provider, Linux, Windows, macOS
Version: 1.2
Created: 07 September 2023
Last Modified: 02 July 2025

Procedure Examples

ID Name Description
C0027 C0027

During C0027, Scattered Spider impersonated legitimate IT personnel in phone calls to direct victims to download a remote monitoring and management (RMM) tool that would allow the adversary to remotely control their system.[5]

G1046 Storm-1811

Storm-1811 has initiated voice calls with victims posing as IT support to prompt users to download and execute scripts and other tools for initial access.[6][7][8]

Mitigations

ID Mitigation Description
M1017 User Training

Users can be trained to identify and report social engineering techniques and spearphishing attempts, while also being suspicious of and verifying the identify of callers.[9]

Detection Strategy

ID Name Analytic ID Analytic Description
DET0245 Detection Strategy for Spearphishing Voice across OS platforms AN0683

Monitor call log records from corporate devices for unusual or unauthorized numbers, especially repeated calls to/from known malicious phone numbers. Correlate with subsequent system events (e.g., browser navigation, remote management tool execution).

AN0684

Audit VoIP/SIP logs for suspicious outbound calls or call setup messages to unusual endpoints. Correlate with user activity such as browser execution or package installation following the call.

AN0685

Monitor Facetime, iMessage, or SIP client logs for anomalous voice call attempts. Link to subsequent user execution events (downloads, RMM installs) triggered post-call.

AN0686

Correlate MFA push fatigue or unusual consent grant attempts with call activity where adversaries may have socially engineered the user over voice.

References