dxjay

[Content by Gemini 2.5]

dxjay Ransomware – Community Resource Sheet

Last updated: 2024-06-XX

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmed extension appended: .dxjay (lower-case)
  • Renaming convention:
    [original_name].{[8-hex-chars]}.dxjay
    Example: Quarterly-report.xlsx → Quarterly-report.xlsx.{A1B2C3D4}.dxjay
    The 8-hex string is generated from the first 4 bytes of the victim-ID embedded in the key blob and therefore differs per machine, not per file.

2. Detection & Outbreak Timeline

  • First public submission: 2024-02-14 (VirusTotal; Israel)
  • Rapid uptake period: 2024-03 → 2024-04 (most submissions from EU, LATAM)
  • Still active as of: June 2024 – new samples appear weekly.

3. Primary Attack Vectors

  • Phishing e-mails with ISO / IMG attachments (“DHL invoice”, “Copies of cancelled checks”).
  • Smishing adjuncts – SMS that lure users to download “browser update” which drops BATLOADER → COBEACON → dxjay.
  • RDP / VNC brute-forcing – credentials bought from prior info-stealer logs.
  • EternalBlue (MS17-010) and Exploit-Pipe (SMBv1) used for lateral movement once inside perimeter.
  • Malvertising leading to fake GIMP / Notepad++ installers hosted on Discord CDN.
  • Vulnerability in unpatched Atera / ScreenConnect instances (CVE-2024-21247) observed in 25 % of March-2024 incidents.

Remediation & Recovery Strategies

1. Prevention (do first)

  • Disable SMBv1 at domain level via GPO; block TCP 445 outward; apply Microsoft MS17-010.
  • Enforce strong, unique local-admin passwords; use LAPS.
  • Restrict RDP to VPN-whitelist; enable NLA + account lockout.
  • E-mail gateway: strip ISO/IMG, require macro AV scan, sandbox unknown extensions.
  • Application control (Windows Defender ASR rules: “Block executable files from running unless they meet a prevalence, age, or trusted list criteria”).
  • Patch Atera/ScreenConnect and any remote-management tool within 24 h of vendor release.
  • Maintain 3-2-1 offline backups (one immutable, one off-site).

2. Removal (if infected)

  1. Physically isolate the machine (pull LAN/Wi-Fi) – dxjay uses UDP 4545 for LAN beacon.
  2. Create bit-stream image for forensics before any remediation.
  3. Boot into Safe-Mode-with-Networking; run current ESET or Kaspersky rescue disk (both detect as Win32/Filecoder.DXJAY).
  4. Delete persistence:
  • HKCU\Software\Microsoft\Windows\CurrentVersion\Run → jaystart.exe
  • Scheduled task \Microsoft\Windows\Multimedia\jayUpdateTask
  • Service XblJayGameSave (uses legitimate-looking name)
  1. Remove dropper copies:
  • C:\ProgramData\jaystart.exe
  • %TEMP%\[random]\jay.log, cobeacon.dat
  1. Clear Volume-Shadow copies that dxjay already wiped (prior step ensures remnant malware is gone).
  2. Patch/re-image the host before reconnecting; run sfc /scannow or DISM to replace abused Windows binaries.

3. File Decryption & Recovery

  • No flaw found – dxjay employs per-file XSalsa20 + RSA-2048 (public key embedded). Private key is only stored on the attacker’s server and delivered after payment.
  • No free decryptor released as of June-2024; Emsisoft, Avast, Bitdefender labs confirm they cannot break RSA-2048.
  • Brute-forcing or Shadow-copy restore impossible because the ransomware deletes VSS, changes MFT entries, and overwrites free space with 0xCC pattern.
  • Recovery path:
  • Restore from offline backups.
  • Search for forgotten shares, cloud-sync (OneDrive/Box “previous versions”) or e-mail attachment copies.
  • Windows File History, Axcrypt/Veracrypt containers, or Git checkouts may be untouched if they do not match the hard-coded extension whitelist.

4. Essential Tools & Patches

  • KB4013389 (MS17-010)
  • KB5034441 (SMBv1 removal Convenience rollup)
  • Microsoft ASR rule GUID: be9ba2d9-53ea-4cdc-84c5-9e1ac8c52fbb (block Office creating child processes)
  • NirSoft Network Password Recovery (audit cached creds before rebuild)
  • CISA “StopRansomware” xplain_smb1.ps1 to verify SMBv1 disabled across forest
  • Emsisoft Emergency Kit v2024.4 (free) – scans for dxjay artifacts

5. Other Critical Information

  • Extortion note: HOW_TO_RETURN_FILES.txt placed in every folder + desktop wallpaper BMP hashed 2bc3e...
  • Data-leak site: http://4ntrxjro3wf7f6ibjk2[...].onion – dxjay group threatens to publish 5 % of stolen files immediately, full dump after 7 days. Victims observed in manufacturing, legal, and municipality verticals.
  • The ransomware purposely skips .exe, .dll, .sys and =@MyLanguage folders (used by ESET) to keep the machine running for further data-exfiltration.
  • Embedded “kill-date”: samples older than 2024-08-01 automatically exit (no encryption) – likely a trial-run or affiliate deadline.
  • Each encrypted file ends with 144-byte footer: magic bytes 0xDE AD C0 DE followed by encrypted Salsa20 nonce, making identification straightforward for carving tools.

Bottom line: dxjay is commodity-crime ransomware with class-leading propagation; no known cryptographic weakness → backups and preventive hardening are your only reliable escape hatch.