Sofacy Group Malware Sample 3

Hunt Hypothesis

Sofacy Group is using a custom malware sample to exfiltrate sensitive data from compromised systems. SOC teams should proactively hunt for this behavior in Azure Sentinel to detect and mitigate advanced persistent threat activity early.

YARA Rule

rule Sofacy_Bundestag_Mal3 
{

    meta:
        description = "Sofacy Group Malware Sample 3"
        author = "Florian Roth"
        reference = "http://dokumente.linksfraktion.de/inhalt/report-orig.pdf"
        date = "2015-06-19"
        hash = "5f6b2a0d1d966fc4f1ed292b46240767f4acb06c13512b0061b434ae2a692fa1"
        score = 70
   
    strings:
        $s1 = "shell\\open\\command=\"System Volume Information\\USBGuard.exe\" install" fullword ascii 
        $s2 = ".?AVAgentModuleRemoteKeyLogger@@" fullword ascii 
        $s3 = "<font size=4 color=red>process isn't exist</font>" fullword ascii 
        $s4 = "<font size=4 color=red>process is exist</font>" fullword ascii 
        $s5 = ".winnt.check-fix.com" fullword ascii 
        $s6 = ".update.adobeincorp.com" fullword ascii 
        $s7 = ".microsoft.checkwinframe.com" fullword ascii
        $s8 = "adobeincorp.com" fullword wide 
        $s9 = "# EXC: HttpSender - Cannot create Get Channel!" fullword ascii 
        $x1 = "User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:20.0) Gecko/20100101 Firefox/" wide 
        $x2 = "User-Agent: Mozilla/5.0 (Windows NT 6.; WOW64; rv:20.0) Gecko/20100101 Firefox/2" wide 
        $x3 = "C:\\Windows\\System32\\cmd.exe" fullword wide 
   
    condition:
        uint16(0) == 0x5a4d and filesize < 300KB and ( 2 of ($s*) or ( 1 of ($s*) and all of ($x*) )) 
}

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 12 string patterns in its detection logic.

References

False Positive Guidance

Scenario: Legitimate system update using Microsoft Windows Update
Filter/Exclusion: process.name != "wuauclt.exe" or process.name != "svchost.exe" (if specifically associated with Windows Update)
Scenario: Scheduled backup job using Veeam Backup & Replication
Filter/Exclusion: process.name != "vmbackup.exe" or process.name != "Veeam.Backup.exe"
Scenario: Administrative task using PowerShell for system configuration
Filter/Exclusion: process.name != "powershell.exe" or process.name != "pwsh.exe" with a check for process.parent.name != "task scheduler"
Scenario: Antivirus scan initiated by Microsoft Defender ATP
Filter/Exclusion: process.name != "MsMpEng.exe" or process.name != "mpsvc.exe"
Scenario: Log collection using Splunk Forwarder
Filter/Exclusion: process.name != "splunkforwarder.exe" or process.name != "splunkd.exe" with a check for process.parent.name != "splunkforwarder.exe"