Record Audio

Hunt Hypothesis

The detection rule identifies potential adversary behavior involving the recording of audio, which may indicate reconnaissance or data exfiltration activities. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate potential espionage or surveillance threats early.

YARA Rule

rule sniff_audio {
    meta:
        author = "x0r"
        description = "Record Audio"
        version = "0.1"
    strings:
        $f1 = "winmm.dll" nocase
        $c1 = "waveInStart"
        $c2 = "waveInReset"
        $c3 = "waveInAddBuffer"
        $c4 = "waveInOpen"
        $c5 = "waveInClose"
    condition:
        $f1 and 2 of ($c*)
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 6 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: A system administrator is using VoIP Spy to monitor internal calls for compliance purposes.
  Filter/Exclusion: Exclude processes associated with VoIP Spy by checking the process name or using a custom field for known compliance tools.

• Scenario: A scheduled job runs PowerShell scripts to generate audio files for automated testing.
  Filter/Exclusion: Exclude processes initiated by scheduled tasks using the Task Scheduler name or check for script paths in known testing directories.

• Scenario: An IT team uses Zoom for internal meetings and occasionally records sessions for training.
  Filter/Exclusion: Exclude processes related to Zoom by checking the process name or using a custom field for known conferencing applications.

• Scenario: A developer uses Audacity to edit audio files as part of a media project.
  Filter/Exclusion: Exclude processes associated with Audacity by checking the process name or file extensions related to audio editing.

• Scenario: A system update or patching task uses Windows Audio Session API to test audio drivers.
  Filter/Exclusion: Exclude processes initiated by Windows Update or System Configuration Manager using process parent or service name.