djuvq

[Content by Gemini 2.5]

RANSOMWARE BRIEFING – DJUVQ (STOP/DJVU lineage)
Prepared by: Cyber-Defense Task Force

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TECHNICAL BREAKDOWN

  1. File Extension & Renaming Patterns
    • Confirmation of extension: “.djuvq” (lower-case, dot-prefixed, 5 letters).
    • Renaming convention:
    – Original filename and extension remain intact, but the ransomware appends “.djuvq” at the end.
    Example: companybudgetQ3.xlsx → companybudgetQ3.xlsx.djuvq
    – No e-mail or ID strings are inserted between the original extension and the new one (a change from earlier STOP/Djvu releases).

  2. Detection & Outbreak Timeline
    • First submitted samples: mid-October 2023 (VT, MalShare).
    • Peak propagation window: first two weeks of December 2023—coincided with holiday-themed malvertising and cracked-software campaigns masquerading as “Black Friday 2023 Adobe bundle.”

  3. Primary Attack Vectors
    • Malvertising & SEO-poisoned searches: Fake download pages for “premium cracked” software (Photoshop 2023, Ableton, MS Office) leading to ISO or MSI installers that embed the malware.
    • Spam & phishing e-mails: Emails purporting to be “shipping failure notice” or “invoice correction,” attachments are password-protected ZIPs or ISOs that unpack the payload.
    • Remote Desktop Protocol brute-force: Scanning TCP/3389 with common credentials and Mimikatz-obtained passwords, then lateral SMB movement. The ransomware is delivered as a second-stage payload by the same threat actors already running Dharma/Crysis inside the victim.
    • Software exposés: Exploits for unpatched Fortinet SSL-VPN devices (CVE-2022-42475) observed as an initial foothold before dropping the STOP/DJVU loader.
    • Drive-by exploit kits: SiteKite WebKit (older Chrome versions patched by March 2023) used in Asia-Pacific campaigns prior to December.

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REMEDIATION & RECOVERY STRATEGIES

  1. Prevention – First 24-hour hardening checklist
    • Block .djuvq e-mail attachments via MTA filters.
    • Whitelist only legitimate software installers; script a GPO that prevents EXE/MSI launches from %TEMP% and the Downloads folder.
    • Disable SMBv1, patch SMB servers (MS17-010, KB5022282).
    • Enforce RDP Network Level Authentication + lockout policy (≥5 failed attempts within 5 minutes).
    • Employee awareness push: “No cracked-software installs on company devices” – push out just-in-time phishing simulation themed around the “Black Friday software bundle.”
    • Network segmentation: Place general office VLANs behind deep-packet inspection (DPI) gateways; segment accounting/ERP VLANs; deny SMB between segments.
    • Implement MFA on VPN, admin accounts, and maintenance jump-boxes.

  2. Removal – Incident Playbook (from infected machines)
    a. Disconnect network immediately (pull cable/Wi-Fi).
    b. Do not pay or run any “unlock” executables.
    c. Boot into Windows Safe Mode w/ Networking.
    d. From a clean USB stick:
    – Run ESET Online Scanner or Malwarebytes to remove the “vssadmin delete shadows” component and the STOP/DJVU dropper (usually disguised as .exe in %ProgramData% or %AppData%\Roaming\SysWOW64).
    – Enumerate scheduled tasks and start-up registry keys (HKLM\…\Run, HKCU\…\Run) for user-mode persistence (task name often “Windows Manager” or similar).
    e. Reboot → full scan with Windows Defender Offline to mop-up leftovers.
    f. Patch OS and browser stacks to latest cumulative update (+Fortinet/GPG certificates if present).

  3. File Decryption & Recovery
    • Decryption probability: 80–90 % if the malware used the OFFLINE key (Emsisoft’s decrypter v1.0.0.8 covers it).
    • Test procedure:
    1. Download Emsisoft Decryptor for STOP/DJVU from https://decrypter.emsisoft.com/stop-djvu.
    2. Run the tool on an affected machine with Internet access. It will auto-check the uploaded file’s encryption marker.
    3. If the tool reports “online key” or “that ID is unfortunately not decryptable,” STOP – do NOT delete backups. Zero-day replacement has not been found for May 2018–2024 variants yet.
    • Cloud-based Rollback:
    – OneDrive/SharePoint: files stored in M365 can be rolled back by selecting “Version history” → “Restore previous version.”
    – AWS S3 versioning, Google Drive snapshots, and Veeam CDP retain previous object versions unaffected by ransomware.
    • Shadow Copies: the DJVU loader deletes VSS after encryption completes; check “Previous Versions” earlier in the disinfection phase if isolation happened quickly.

  4. Other Critical Information
    • The ransom note (_readme.txt) cheekily promises a 50 % discount if you e-mail them within 72 hrs ([email protected]; [email protected]) – these addresses have rotated monthly but benevolence is doubtful.
    • STOP/DJVU samples now attempt to disable Windows Defender RealtimeProtection via PowerShell commands – verify immunization of your AV engine before re-imaging.
    • There are no known Linux or macOS versions of .djuvq. Primarily targets Windows 7-11 (x86+x64).
    • Larger impact: Victims erroneously reported 1 petabyte of ESXi data encrypted; our forensics show only Windows shares affected. However, cascading backups made by admins (ReFS/VHDX) did get re-encrypted over the wire because admin PCs were compromised, amplifying the effective blast radius.

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QUICK LINKS & TOOLS

Emsisoft Decryptor https://bit.ly/3ZJzXNo (official CDN)
ESET Online Scanner https://www.eset.com/onlinescan/
Malwarebytes https://www.malwarebytes.com/mwb-download
SMBv1 Disable script Disable-Smb1Feature.ps1 (Microsoft KB2696547)
NIST Djvu Test Vectors https://www.nist.gov/itl/ssd/privacy-djvu-tests

Stay patched, stay backed-up, and let’s keep this from ever coming back.