VxTravJack883

Hunt Hypothesis

This YARA rule targets specific memory patterns associated with the VxTravJack883 malware family, indicating the presence of a known threat actor or tooling within the environment. Proactively hunting for this signature allows the SOC team to identify low-severity intrusions that may have evaded traditional network-based detections, enabling early containment before the adversary establishes persistence or exfiltrates data.

YARA Rule

rule VxTravJack883
{
      meta:
		author="malware-lu"
strings:
		$a0 = { EB ?? 9C 9E 26 [2] 51 04 ?? 7D ?? 00 ?? 2E [4] 8C C8 8E C0 8E D8 80 [4] 74 ?? 8A [3] BB [2] 8A ?? 32 C2 88 ?? FE C2 43 81 }

condition:
		$a0 at pe.entry_point
}

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 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: A developer or DevOps engineer runs a custom Python script or PowerShell wrapper that embeds a specific string constant (e.g., "VxTravJack883") as a version tag, build identifier, or internal project codename within a legitimate build artifact or configuration file.

  • Filter/Exclusion: Exclude files with extensions .py, .ps1, .json, .yaml, or .xml located in standard source control directories (e.g., C:\src\, D:\projects\) or exclude processes named python.exe or pwsh.exe when the file path contains keywords like build, config, or src.

• Scenario: An enterprise application or middleware (such as a custom ERP module or API gateway) uses “VxTravJack883” as a default session token, API key, or internal service identifier that is written to temporary files or log entries during routine health checks or service startup.

  • Filter/Exclusion: Exclude file paths under C:\ProgramData\, C:\Temp\, or C:\Logs\ for known enterprise application service names (e.g., svc-erp.exe, api-gateway.exe). Additionally, exclude if the file size is less than 4KB and the last modified time is within the last 15 minutes.

• Scenario: A scheduled maintenance job or backup utility creates a temporary archive or metadata file that includes a checksum or hash label derived from an internal naming convention that coincidentally matches the string “VxTravJack883” (e.g., used as a salt or identifier in a proprietary backup format).

  • Filter/Exclusion: Exclude files with extensions .bak, .tmp, .log, or .dat that are owned by service accounts (e.g., svc-backup,