Detects sample mentioned in the Dubnium Report

Hunt Hypothesis

The hypothesis is that the detected sample is associated with the Dubnium Report, indicating potential adversarial activity linked to known malicious behavior. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage threats tied to this specific malware family.

YARA Rule

rule Dubnium_Sample_1
{

    meta:
        description = "Detects sample mentioned in the Dubnium Report"
        author = "Florian Roth"
        reference = "https://goo.gl/AW9Cuu"
        date = "2016-06-10"
        hash1 = "839baf85de657b6d6503b6f94054efa8841f667987a9c805eab94a85a859e1ba"

    strings:
        $key1 = "3b840e20e9555e9fb031c4ba1f1747ce25cc1d0ff664be676b9b4a90641ff194" fullword ascii
        $key2 = "90631f686a8c3dbc0703ffa353bc1fdf35774568ac62406f98a13ed8f47595fd" fullword ascii

    condition:
        uint16(0) == 0x5a4d and filesize < 2000KB and all of them
}

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 2 string patterns in its detection logic.

References

• https://goo.gl/AW9Cuu
• Source Rule

False Positive Guidance

• Scenario: Scheduled system backup using Veeam Backup & Replication
  Filter/Exclusion: process.name != "vbm.exe" or process.name != "vmbackup.exe"

• Scenario: Admin performing a disk cleanup using Disk Cleanup tool (cleanmgr.exe)
  Filter/Exclusion: process.name != "cleanmgr.exe" or process.name != "cleanmgr.exe"

• Scenario: Automated log rotation using Logrotate on Linux
  Filter/Exclusion: process.name != "logrotate" or process.name != "logrotate"

• Scenario: User running a legitimate malware analysis tool like Cuckoo Sandbox
  Filter/Exclusion: process.name != "cuckoo" or process.name != "cuckoo-sandbox"

• Scenario: System task scheduled via Task Scheduler to run a legitimate script
  Filter/Exclusion: process.name != "schtasks.exe" or process.name != "taskhost.exe"