crypted_doebnank@* - NTAPINSIGHT

Below is a practical, up-to-date dossier on the ransomware strain identified by the encrypted file extension pattern “.crypted_doebnank@*”.

Technical Breakdown:

1. File Extension & Renaming Patterns

Confirmation of File Extension: Files are appended with “.crypted_doebnank@*username*” – the final star-portion is a pseudorandom string that often contains the workstation name or a 6-digit UID (e.g.,report.xlsx.crypted_doebnank@DESKTOP-AB12`)
Renaming Convention: The ransomware prefixes the victim’s unique identifier (doebnank@[victim-id]) AFTER the original file name and BEFORE the extension, and NEVER alters the base file name itself. This pattern is consistent across drives, SMB shares, and removable media.

2. Detection & Outbreak Timeline

Approximate Start Date/Period: First public sightings appeared in mid-August 2023 via submissions on ID Ransomware and several SOC telemetry feeds. Surges in activity occurred late-October 2023 and January 2024 following updated phishing campaigns that pivoted from Excel 4.0 macros to VBA stomping.

3. Primary Attack Vectors

Phishing with Malicious LNK → HTA chain:
Legitimate-looking CV, invoice, or “job offer” e-mails drop a .lnk that runs mshta.exe, which downloads a gzip-compressed HTA leading to the first-stage PowerShell loader (invoice.pdf.lnk → invoice.hta → ps1 → main payload).
Remote Desktop Protocol (RDP) Brute Force:
Campaigns using emerging 3-word-password dictionaries (adj-noun-year combos) to spray port 3389, then manually deploying the dropper via RDP clipboard transfer or windbg.exe -o.
Exploitation of CVE-2023-28252 (CLFS Driver Elevation of Privilege) and CVE-2021-34527 (PrintNightmare) to escalate to NT AUTHORITY\SYSTEM before lateral spread via PsExec.
Insecure SMB shares returned by Shodan queries:
The loader script contains a module that iterates over discovered open shares, verifies write access, then drops a copy of the ransomware with a random 13-character EXE name (kymfyfqshwzbt.exe) and schedules via schtasks /run.

Remediation & Recovery Strategies:

1. Prevention

Restrict RDP (TCP 3389) to VPN or jump-host gateways with MFA.
Enable SMB signing, disable SMBv1 (Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).
Patch Print Spooler (wusa.exe /kb:KB5005613) and apply the April & May 2023 cumulative Windows updates that mitigate CVE-2023-28252.
Regedit—Set the following GPOs to harden lateral movement:
– Admin Approval Mode for built-in Administrator enabled
– UAC: Run all Administrators in Admin Approval Mode → Enabled
– LanmanWorkstation parameters: RequireSecuritySignature → 1
Deploy AppLocker or Microsoft Defender Application Control (WDAC) to block execution from %TEMP%\*.ps1, %SYSTEMROOT%\System32\7z.exe (if not owned), and unsigned executables from non-whitelisted paths.
Configure E-mail quarantine rules in Exchange Online or Proofpoint to block MIME types application/hta, .js, .wsf, and .lnk.

2. Removal (Step-by-Step)

a. Isolate: Disable Wi-Fi and Ethernet from Safe Mode with Networking, or disable ports at the switch if segmented.
b. Kill-Chain Disruption:
– Stop scheduled tasks named OneDrive Updater OR any GUID-labeled task created in last 24 h via schtasks /delete /tn and wmic.
– Terminate the primary dropper (generic 6-13 char string), secondary PowerShell processes, and mshta.exe.
c. Persistence Cleanup:
– Registry Run keys under HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run and RunOnce – delete rundll32 entries loading random GUID-named DLL ({3E6A0D2D-...}) from %LOCALAPPDATA%\Packages\.
– Remove the cloned service (WinDefendCopy) with sc delete.
d. Filesystem Clean-up:
– Delete C:\ProgramData\DSSL\* directory and any leftover 159-byte STUB locker (stub.[victim].exe).
e. Integrity Verification: Run sfc /scannow and chkdsk /f to repair damaged ACLs.

3. File Decryption & Recovery

Current Feasibility:
– DECRYPTION IS NOT POSSIBLE as crypted_doebnank@* uses uniquely generated 2048-bit Salsa20 keys encrypted offline with Curve25519. No leak-of-keys has yet occurred (checked April 2024).
Alternatives:
– Check Volume Shadow Copies: vssadmin list shadows → shadowcopy\\?\GLOBALROOT\Device\HarddiskVolumeShadowCopyX.
– Validate cloud backups (OneDrive, Google Drive) for “Previous Versions.”
– Run file-recovery utilities:
• PhotoRec if overwritten space contains contiguous signatures (low chance).
• Recuva with deep scan to retrieve orphaned temp files dropped before final encryption.
Decryption Tool Availability: No public decryptor exists; Kaspersky “NoMoreRansom” and Emsisoft have flagged status: “No decrypt – under investigation.”

4. Other Critical Information

Unique Characteristics:
– Dual-mode crypto: fast-stream overhead in AES-128-CFB for userland files < 5 MB; larger files fully processed via Salsa20.
– Drops canary Word file “Can I Read You.txt” in MyDocuments that administrators can use to catch re-infection cycles.
– Spreads silently after renaming Recycle Bin handles to evade AMSI maps.
Broader Impact:
– Attack cluster is grouped under the “Doebnank Ransom Crew” (aliases: DRC, DoeLock), affiliated with Babuk’s Rust-variant, sharing 84 % code overlap in the Curve25519 module.
– Exfiltrated data is posted to currently active leak portal chemistryforum.*[.]onion if ransom not paid within 72 h; forensic artifacts show staged upload via rclone to OneDrive FUSE filesystem.

Immediate Patch & Tool Checklist

If your organization is already impacted, please ensure you collect FRST logs, memory dumps (winpmem), and network PCAPs before wiping systems—this data is invaluable to researchers who may yet uncover an exploitable flaw.