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Introduction:
A novel social engineering attack vector has emerged in the wild, leveraging trusted Zoom meeting links combined with an audio-based psychological trigger. The attacker initiates a fake meeting audio glitch – a woman’s voice asking “Hello? Hello? Can you hear me?” – while simultaneously displaying a malicious overlay or prompt on the victim’s screen. This technique, suspected to be associated with APT groups like Lazarus, manipulates user curiosity and troubleshooting reflexes to execute arbitrary code, capture credentials, or deploy remote access trojans (RATs).
Learning Objectives:
- Identify and analyze the Zoom audio lure technique and its associated Indicators of Compromise (IoCs)
- Apply forensic commands on Linux and Windows to detect malicious processes, network connections, and file artifacts
- Implement mitigation strategies including Zoom security hardening, API access controls, and user awareness training
You Should Know:
- Forensic Analysis of the Zoom Lure – Process & Network Investigation
This attack typically exploits the Zoom meeting client or a fake meeting webpage. When a user clicks the malicious meeting link, a pre-recorded audio file plays (“Hello? Can you hear me?”) while a fake error dialog or consent prompt appears (e.g., “Audio driver update required” or “Codec missing”). If the user interacts, a payload downloads and executes. Below are step-by-step commands to detect anomalous activity post-click.
Step-by-step guide for Linux:
List all running processes and grep for Zoom or suspicious names ps aux | grep -i zoom Check for unexpected network connections established by Zoom sudo netstat -tunap | grep -i zoom Monitor real-time process creation (requires auditd or sysdig) sudo auditctl -a always,exit -F arch=b64 -S execve -k process_exec sudo ausearch -k process_exec --format raw | tail -20 Capture DNS queries to detect C2 domains (using tcpdump) sudo tcpdump -i eth0 -n 'udp port 53' -vvv
Step-by-step guide for Windows (PowerShell as Admin):
List all Zoom processes with full details
Get-Process -Name zoom | Select-Object Id, ProcessName, StartTime, Path
Check for suspicious child processes spawned by Zoom (e.g., cmd, powershell, wscript)
Get-WmiObject Win32_Process | Where-Object {$_.ParentProcessId -eq (Get-Process -Name zoom).Id} | Format-List
Examine network connections from Zoom process
netstat -ano | findstr <Zoom_PID>
Query Windows Event Log for process creation (Event ID 4688)
Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4688} | Where-Object {$_.Properties[bash].Value -like 'zoom'} | Format-List
2. Capturing and Analyzing the Malicious Payload Delivery
The lure often uses a steganographic or encoded payload embedded in a fake “audio driver” update. Attackers may also abuse Zoom’s built-in file transfer or meeting chat to drop malware. Below are methods to intercept and analyze the payload.
Step-by-step guide:
- Use a sandboxed environment (e.g., Cuckoo, CAPE) or a Windows/Linux VM with network isolation.
- Configure a local proxy (Burp Suite, mitmproxy) to intercept traffic when clicking the lure link.
- For Windows, enable PowerShell script block logging:
Set-ItemProperty -Path "HKLM:\SOFTWARE\Policies\Microsoft\Windows\PowerShell\ScriptBlockLogging" -Name "EnableScriptBlockLogging" -Value 1
- For Linux, use strace to monitor Zoom child processes:
strace -f -e trace=execve -p $(pgrep zoom) 2>&1 | tee zoom_trace.log
- Extract any downloaded files from %TEMP% or /tmp and submit to VirusTotal or ANY.RUN.
- Hardening Zoom Against Social Engineering & Audio Lures
Organizations must configure Zoom security settings to block external meeting invitations, disable file transfer, and restrict remote control. Additionally, API security for Zoom’s REST API prevents attackers from automating meeting creation or user enumeration.
Step-by-step guide for Zoom Admin Portal:
- Navigate to Admin > Account Management > Account Settings > Meeting.
- Disable “File transfer” and “Screen sharing for external users”.
- Enable “Waiting room” for all external participants.
- Under Security, enable “Block users from joining meeting before host” and “Require a passcode for instant meetings”.
- For API security, rotate your JWT token or use OAuth app with least privilege:
Example: Revoke all active Zoom API tokens via cURL curl -X DELETE https://api.zoom.us/v2/users/me/tokens \ -H "Authorization: Bearer <Your_OAuth_Token>"
Step-by-step guide for Windows Group Policy (for Zoom MSI install):
– Download Zoom ADMX templates and import to C:\Windows\PolicyDefinitions.
– Enable policy: Disable automatic audio device selection and Disable remote control by default.
– Deploy via gpupdate /force.
- Cloud Hardening for Zoom Integrations (Azure AD / Okta)
Many enterprises use SSO with Zoom. Attackers who compromise a Zoom meeting link may also attempt token theft. Implement conditional access policies to restrict Zoom access to compliant devices.
Step-by-step guide for Azure AD:
- Go to Azure AD > Security > Conditional Access > New policy.
- Assign to “Zoom” cloud app.
- Set grant control: “Require device to be marked as compliant” and “Require hybrid Azure AD joined”.
- Session control: “Use app enforced restrictions” to prevent file downloads.
- For Linux-based cloud workloads, use `az cli` to audit Zoom enterprise application sign-ins:
az monitor activity-log list --resource-group <RG> --query "[?contains(operationName.value, 'zoom')]"
- Vulnerability Exploitation & Mitigation – Fake Audio Codec Scenario
The “Can you hear me?” lure often leads to a fake codec download (e.g., ZoomAudioCodec.exe). This executable exploits CVE-2023-28531 (an older Zoom RCE) or similar. Mitigation includes patch management and application control.
Step-by-step guide to mitigate via AppLocker (Windows):
Create default rules to block execution from Temp and Downloads New-AppLockerPolicy -RuleType Exe -User Everyone -Path "%USERPROFILE%\Downloads\" -Action Deny Set-AppLockerPolicy -Policy XmlFile -Merge Apply policy gpupdate /force
For Linux, use `fapolicyd` to whitelist only signed Zoom binaries:
sudo dnf install fapolicyd sudo fapolicyd-cli --file add /opt/zoom/zoom --trust-file sudo systemctl enable fapolicyd --now
- API Security & Webhook Abuse in Zoom Apps
Attackers can register a malicious Zoom App that requests `meeting:participant:audio` scope to inject synthetic audio into meetings. This is a newer vector. Defenders must audit existing Zoom Apps and webhooks.
Step-by-step guide to audit Zoom Apps via API:
List all installed apps for your Zoom account
curl -X GET "https://api.zoom.us/v2/users/me/apps" \
-H "Authorization: Bearer <ACCESS_TOKEN>" | jq '.apps[] | {name, scopes, status}'
Revoke a malicious app
curl -X DELETE "https://api.zoom.us/v2/users/me/apps/<APP_ID>" \
-H "Authorization: Bearer <ACCESS_TOKEN>"
– Additionally, monitor Zoom webhook logs for unexpected `meeting.participant_joined` events with suspicious user agents.
7. User Awareness Training & Simulated Attack Modules
Given the psychological effectiveness of the audio lure, training must include realistic simulations. Develop a training course module with the following PowerShell script to simulate a benign “audio glitch” popup for internal testing (do not deploy without consent).
Simulated Training Lure (Windows)
Add-Type -AssemblyName System.Windows.Forms
$msgBoxInput = [System.Windows.Forms.MessageBox]::Show('Hello? Can you hear me? Audio driver may be outdated. Click OK to run diagnostics.','Zoom Audio Alert','OKCancel','Warning')
if ($msgBoxInput -eq 'OK') {
Write-Host "[bash] User clicked OK - This would have downloaded malware. Please report to security team."
In real training, redirect to a safe educational page
Start-Process "https://company-training.com/zoom-lure-explained"
}
What Undercode Say:
- Key Takeaway 1: The “Hello? Can you hear me?” lure exploits human troubleshooting instinct – users instinctively click “OK” or “Fix” to restore audio. This bypasses even technical users if they are not explicitly trained on audio-based social engineering.
- Key Takeaway 2: API-level controls and conditional access policies are as critical as endpoint detection. Attackers increasingly abuse legitimate Zoom APIs and webhooks to automate phishing at scale.
- Key Takeaway 3: No single tool detects this; a layered defense combining network forensics (tcpdump, netstat), endpoint process monitoring (auditd, Sysmon), and Zoom admin hardening is required. The Lazarus group has used similar audio lures in the past, indicating this is likely an ongoing APT campaign.
Prediction:
Within the next six months, we will see a surge of AI-generated voice clones replacing the generic “woman’s voice” in Zoom lures – personalized to the victim’s known contacts or company executives. Combined with deepfake video overlays, this will render traditional audio-based suspicion obsolete. Defenders will need to adopt real-time voice biometrics and meeting integrity checks, shifting the arms race toward AI-driven anomaly detection in collaboration platforms.
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Reported By: Pallis New – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
