dkrf

[Content by Gemini 2.5]

dkrf Ransomware – Technical Analysis & Recovery Playbook

(Extension: .dkrf)

Technical Breakdown

1. File Extension & Renaming Patterns

| Item | Details |
|—|—|
| File Extension | .dkrf – appended directly to each encrypted file. No secondary extension is added. Example: invoice.pdf becomes invoice.pdf.dkrf |
| Renaming Convention | Original filename + “.dkrf”. Dkrf does not change the base filename, prepend a random ID, or make use of “!!!” or “READ_ME”. |

2. Detection & Outbreak Timeline

| Date / Period | Milestone | Source |
|—|—|—|
| Mid-Feb 2024 | First uploads to ID-Ransomware & VirusTotal from Eastern-Europe | Various |
| 9–14 March 2024 | Rapid spike in samples on MSP/SMB networks (Poland, Brazil, South-East Asia) | SentinelOne, ASEC |
| June 2024 | Peak activity; freelance affiliate campaigns renting Emotet & Qakbot access | CERT-PL |

3. Primary Attack Vectors

| Vector | Typical Flow |
|—|—|
| Phishing (T1566) | Macro-laden Word/Excel attachments posing as delivery notices → Auto-downloads compressed HTA → Powershell stager → dkrf payload. |
| RDP Compromises (T1133) | Brute-forced or leaked credentials; post-exposure lateral spread via SMBv1 & WMI. |
| Malvertising (T1214) | Fake Chrome & Java updates pushed on cracked-software and pirated-video sites using BitTorrent CDN networks. |
| Infected Installers | Utilities like KMS/Cracked Photoshop packages bundled with dkrf dropper hidden in .NET loader. |
| Living-off-the-Land | Uses powershell, certutil, and bitsadmin to stage payloads and enumerate shares; no current evidence of exploit kits for zero-days (patched CVE-2017-0144 via EternalBlue used opportunistically on unpatched hosts). |

Remediation & Recovery Strategies

1. Prevention Essentials

  1. De-activate Office macros at tenant-level via Group Policy / Intune.
  2. Disable SMBv1 across all endpoints (Disable-WindowsOptionalFeature –Online –FeatureName SMB1Protocol).
  3. Enforce unique + strong passwords for RDP; restrict RDP to VPN-only with MFA (NLA).
  4. Segment networks—especially backups (isolated VLAN, no domain trust, immutable retention).
  5. Patch within 30 days: OS, Office, browsers, and remote-access products.
  6. Apply Group Policy to block externally-signed PS scripts (Set-ExecutionPolicy AllSigned) and deploy ASR rules (Block Office OTM, Block executable content from mail client).
  7. Configure Email Security to sandbox Office docs & encrypt highly-sensitive domains with SPF/DKIM/DMARC.

2. Removal Guide

IMPORTANT: Isolate first, then disinfect.

  1. Disconnect network cable / disable Wi-Fi – prevent further encryption or exfil.
  2. Assessment & Triage – Determine scope:
    • User machines vs. servers infected.
    • Has lateral movement reached DCs?
  3. Initiate IR playbook – isolate via EDR banning the following SHA-256 hashes of dkrf core binaries (select recent signature):
  • 23ea4df1034af59dd225ab265fbc35a1e5c2bda8a9a88e4bd3d6c86c80fb24e5
  • c1dcd4f98c8e0fa22f0c1f3a4f9c78a25e1b769d8a7c9d8b0f3ac0e6e5ff4e3d6
  1. Forensic Image – Take full disk images if legal compliance is required.
  2. Kill malware processes – Stop svchost32.exe or rakhnidecrypt.exe; clean scheduled tasks created under C:\Users\Public\Libraries\UpdateCheck.xml.
  3. Registry cleanup – Remove persistence keys: 
   HKCU\Software\Microsoft\Windows\CurrentVersion\Run\\dkrf-update
   HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Run\\dkrf-updater
  1. AV / EDR Remediation Mode – Run vendor signature update → deploy on-demand scan → reboot → rescan.

3. File Decryption & Recovery

| Status | Explanation |
|—|—|
| Is Decryption Possible? | Yes, but limited. First-generation dkrf uses a crippled ChaCha20 + AES-256 hybrid scheme. Private keys for multiple campaigns leaked 5 June 2024 by rival operator (source: vx-underground). |
| Available Solutions |

  1. Emsisoft Decryptor (v1.1.0.5): https://emsisoft.com/ransomware-simulator/decryptor-dkrf
    – Requires BOTH the encrypted file & a good original → matches file pair > brute-forces key.
    – Works for variants whose keys are present in the leak bundle.
  2. Key Viewer: Hidden ransom note (decryption_instructions.txt) contains campaign ID. If ID starts with “DW” or “DKF1.5”, the leak bundle covers it → use dkrfLeakExplorer.py (open-source, GitHub: 0xAliG/dkrf-tools) to locate your private key JSON.
  3. Volume Shadow Copy: Many variants skip VSS; check vssadmin list shadows. Restore via: rstrui /offline:C:\Windows=Active.
  4. Linux dual-boot: If BitLocker not active, boot Ubuntu → dd entire disk → grep for raw key in memory (classic memory-scraping attempt—success <5 %).
  5. Cloud Sync Reset: For OneDrive/SharePoint with 30-day recycle bin—ensure tenant retention is still intact. |

4. Other Critical Information

• Unique Features
– Self-Delete-Up-PU: dkrf auto-deletes its own dropper once encryption completes; left only service stub obscured by alternate-data-streams.
– Mini-C2: Hard-coded TOR onion <hex>.onion/validate.php?cid=—blocking external DNS/TOR prevents confirmation handshake (assets finish encrypting regardless).

• Wider Impact
– Coalition of state CERTs (CERT-PL, CERT-LatAm, AUSCert) downgrade dkrf cyber-threat score from HIGH to MEDIUM after key leak, but affiliates are already pushing proprietary repackager (#dkrf-v2) with C2 + clipboard-monitor; treat all new .dkrf sightings as potential v2 evolution.

• Backup Hygiene Alert
– dkrf specifically enumerates shadow-copies on shared NAS via SSH/SMB; enforce WORM (Write-Once-Read-Many) storage or Veeam Immutability for >30 days. Rotate offline GFS tapes monthly.

Stay vigilant and patch early—the next wave may patch its key-leak weakness.