Most likely a malicious file acrotray in SFX RAR / CloudDuke APT 5442.1.exe, 5442.2.exe

Hunt Hypothesis

The detection identifies potential malicious execution of SFX RAR archives containing CloudDuke APT payloads, specifically 5442.1.exe and 5442.2.exe, which are associated with advanced persistent threat activity. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage compromises by adversaries leveraging these sophisticated delivery methods.

YARA Rule

rule SFXRAR_Acrotray
{

    meta:
        description = "Most likely a malicious file acrotray in SFX RAR / CloudDuke APT 5442.1.exe, 5442.2.exe"
        author = "Florian Roth"
        reference = "https://www.f-secure.com/weblog/archives/00002822.html"
        date = "2015-07-22"
        super_rule = 1
        score = 70
        hash1 = "51e713c7247f978f5836133dd0b8f9fb229e6594763adda59951556e1df5ee57"
        hash2 = "5d695ff02202808805da942e484caa7c1dc68e6d9c3d77dc383cfa0617e61e48"
        hash3 = "56531cc133e7a760b238aadc5b7a622cd11c835a3e6b78079d825d417fb02198"

    strings:
        $s1 = "winrarsfxmappingfile.tmp" fullword wide /* PEStudio Blacklist: strings */
        $s2 = "GETPASSWORD1" fullword wide /* PEStudio Blacklist: strings */
        $s3 = "acrotray.exe" fullword ascii
        $s4 = "CryptUnprotectMemory failed" fullword wide /* PEStudio Blacklist: strings */

    condition:
        uint16(0) == 0x5a4d and filesize < 2449KB 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 4 string patterns in its detection logic.

References

False Positive Guidance

Scenario: Legitimate Adobe Acrobat Tray Application
Description: The acrotray.exe process is a legitimate part of Adobe Acrobat Reader and is often found in enterprise environments.
Filter/Exclusion: Check the file path against known Adobe installation directories (e.g., C:\Program Files (x86)\Adobe\Acrobat Reader DC\Reader\acrotray.exe).
Suggested Filter: file_path contains "Adobe\Acrobat Reader"
Scenario: Scheduled Job for File Compression
Description: A scheduled task or script may use RAR compression tools (e.g., rar.exe) to archive files, which could trigger the rule due to the presence of .exe files in the process tree.
Filter/Exclusion: Filter by the parent process name (e.g., schtasks.exe or cmd.exe) and check for known compression tool paths.
Suggested Filter: parent_process_name contains "schtasks.exe" or "cmd.exe"
Scenario: System Update or Patch Deployment
Description: A system update or patch deployment tool (e.g., Microsoft Update, SCCM, or third-party tools) may execute .exe files as part of its deployment process, which could be flagged.
Filter/Exclusion: Check for known update tools in the process tree and verify the file path against enterprise update directories.
Suggested Filter: parent_process_name contains "wusa.exe" or "msiexec.exe"
Scenario: Admin Task for File Extraction
Description: An administrator may use tools like 7-Zip or WinRAR to extract files, which could trigger the rule due to the presence of .exe files in the process tree.
Filter/Exclusion: Filter by the parent process name (e.g., `7