Detects Turla malware (based on sample used in the RUAG APT case)

Hunt Hypothesis

The hypothesis is that the detection identifies potential Turla malware activity associated with the RUAG APT group, leveraging specific indicators observed in the sample. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage Turla infections that may evade traditional detection methods.

YARA Rule

rule Turla_APT_srsvc 
{

    meta:
        description = "Detects Turla malware (based on sample used in the RUAG APT case)"
        author = "Florian Roth"
        family = "Turla"
        reference = "https://www.govcert.admin.ch/blog/22/technical-report-about-the-ruag-espionage-case"
        date = "2016-06-09"
        hash1 = "65996f266166dbb479a42a15a236e6564f0b322d5d68ee546244d7740a21b8f7"
        hash2 = "25c7ff1eb16984a741948f2ec675ab122869b6edea3691b01d69842a53aa3bac"
  
    strings:
        $x1 = "SVCHostServiceDll.dll" fullword ascii
        $s2 = "msimghlp.dll" fullword wide
        $s3 = "srservice" fullword wide
        $s4 = "ModStart" fullword ascii
        $s5 = "ModStop" fullword ascii
    
    condition:
        ( uint16(0) == 0x5a4d and filesize < 20KB and ( 1 of ($x*) or all of ($s*) ) ) or ( 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 5 string patterns in its detection logic.

References

False Positive Guidance

Scenario: A system administrator is using Microsoft Sysinternals Process Explorer to investigate a suspicious process.
Filter/Exclusion: Check for the presence of ProcessExplorer.exe in the process name or command line.
Scenario: A scheduled job runs Windows Task Scheduler to perform routine system maintenance, such as disk cleanup or log rotation.
Filter/Exclusion: Exclude processes initiated by schtasks.exe or check for known maintenance task names in the command line.
Scenario: An IT admin is using PowerShell to run a script that configures system settings or updates software.
Filter/Exclusion: Filter out PowerShell scripts that match known administrative scripts or check for the presence of powershell.exe with a known script path.
Scenario: A user is running 7-Zip to extract a compressed file that contains legitimate configuration files.
Filter/Exclusion: Exclude processes where the executable is 7z.exe or check for known 7-Zip command-line arguments.
Scenario: A developer is using Git to push code changes to a remote repository, which includes files with names similar to Turla indicators.
Filter/Exclusion: Exclude processes initiated by git.exe or check for the presence of a known Git command in the command line.