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_3
{

    meta:
        description = "Detects sample mentioned in the Dubnium Report"
        author = "Florian Roth"
        reference = "https://goo.gl/AW9Cuu"
        date = "2016-06-10"
        hash1 = "caefcdf2b4e5a928cdf9360b70960337f751ec4a5ab8c0b75851fc9a1ab507a8"
        hash2 = "e0362d319a8d0e13eda782a0d8da960dd96043e6cc3500faeae521d1747576e5"
        hash3 = "a77d1c452291a6f2f6ed89a4bac88dd03d38acde709b0061efd9f50e6d9f3827"

    strings:
        $x1 = "copy /y \"%s\" \"%s\" " fullword ascii
        $x2 = "del /f \"%s\" " fullword ascii
        $s1 = "del /f /ah \"%s\" " fullword ascii
        $s2 = "if exist \"%s\" goto Rept " fullword ascii
        $s3 = "\\*.*.lnk" fullword ascii
        $s4 = "Dropped" fullword ascii

    condition:
        uint16(0) == 0x5a4d and filesize < 2000KB and 5 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 6 string patterns in its detection logic.

References

False Positive Guidance

Scenario: Scheduled System Backup Job
Description: A legitimate scheduled backup job runs and generates a file with a name similar to one mentioned in the Dubnium Report.
Filter/Exclusion: Check for file paths containing known backup directories (e.g., /var/backups/, /backup/, or C:\Backup\) and exclude files with .bak, .zip, or .tar.gz extensions.
Scenario: Admin Task for Log Rotation
Description: An administrator runs a log rotation script that temporarily creates files with names matching those in the Dubnium Report.
Filter/Exclusion: Exclude files located in log directories (e.g., /var/log/, /logs/, or C:\Windows\System32\LogFiles\) and filter by file creation time within the last 24 hours.
Scenario: Temporary File Created by a Development Tool
Description: A developer tool (e.g., docker, kubectx, or terraform) creates temporary files with names that match the Dubnium Report.
Filter/Exclusion: Exclude files with temporary file extensions (e.g., .tmp, .swp, .lock) and filter by user context (e.g., uid=1000 or user=dev-team).
Scenario: Artifact from a Security Tool Scan
Description: A security tool (e.g., ClamAV, Sophos, or CrowdStrike) generates a temporary file with a name similar to one in the Dubnium Report during a scan.
Filter/Exclusion: Exclude files created by known security tools (e.g., clamav, sophos, crowdstrike) and filter by process name or parent process.
Scenario: User-Generated File for Testing or Debugging