dfwe

[Content by Gemini 2.5]

Ransomware Profile: DFWE

Technical Breakdown

1. File Extension & Renaming Patterns

  • Core Extension Used: .dfwe is appended to every encrypted file.
  • Typical Rename Pattern:
  • Pre-encryption: Document.docx
  • Post-encryption: Document.docx.dfwe
  • Common prefixes like id-[random_digits], email-[attacker_mail], or [hostname]- may also appear:
    Example: id-VHL924Z.Document.docx.dfwe or [email protected]
  • No visible base-name changes except for the extension ; directory and file names remain intact, which distinguishes DFWE from double-ext payloads such as .locky.docb.

2. Detection & Outbreak Timeline

  • First Public Sightings: Initial DFWE campaigns were recorded in underground credential-marketplaces around late September 2022.
  • Wider Outbreak: Mid-November 2022 when multi-tenant MSPs and educational institutions in North America and Western Europe began reporting clusters.
  • Evolution: Subsequent waves fluctuated every 45–60 days through Q1 2023, with delivery TTPs shifting from e-mail to network-based intrusions.

3. Primary Attack Vectors

  1. Phishing & Weaponized Attachments
    – Emails masquerading as Microsoft Teams, Docusign, and delivery invoices contain ISO/IMG attachments that mount as removable drives.
    – Typical filenames: Invoice_12Oct.2022.img, Notice_Quarantine.iso.
  2. Exploit-Kit Pivot over SMBv1
    – DFWE propagates laterally by leveraging EternalBlue (MS17-010) against unpatched Windows 7/Server 2008 machines once the initial foothold is established.
  3. RDP Brute-forcing & Credential Re-use
    – Attacker-controlled IP ranges repeatedly scan port 3389 for weak passwords; once a domain admin account is obtained, the ransomware is pushed via PSExec.
  4. Software Supply-Chain via Pirated Tools
    – Trojanized versions of Adobe Acrobat Pro, AutoCAD, and KMS activators package DFWE in their installers.
  5. Cloud Storage Poisoning
    – After breaching SaaS OneDrive or Google Drive accounts, DFWE replaces synchronized files with encrypted counterparts, leveraging Microsoft Graph APIs and OAuth tokens it acquired.

Remediation & Recovery Strategies

1. Prevention

| Layer | Action |
|—|—|
| Email / Web | • Block outbound access to .img, .iso, and .vhd at mail-gateway. • Enable Microsoft Defender ASR rules “Block executable files from running unless they meet a prevalence age or trusted list” and “Block credential stealing from the Windows local security authority subsystem”. |
| OS & Services | • Patch every system against MS17-010, MS21-013, and CVE-2022-30190 (Windows MSDT “Follina”). • Disable SMBv1 via Group Policy: Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol. |
| Credential Hygiene | • Force 14-char+ unique passwords and enable Azure AD Smart-Lockout. • Enforce MFA on all privileged accounts, especially RDP jump boxes. |
| Backup Regimen | • 3-2-1: At least three copies, in two different media, one off-site/immutable. • Enable Azure Blob versioning + “Delete Lock” for cloud backups. |
| Logging & Detection | • Enable Sysmon (Event ID 1, 11, 13) to catch the powershell command powershell.exe Copy-Item "dfwe.exe" -Destination "C:\ProgramData" and unusual vssadmin delete shadows. • Run wmic Shadowcopy delete alerts in EDR. |
| Network Segmentation | • VLAN isolate end-user segments from servers. Deny cross-subnet SMB/RDP to everything except authorized jumpstation. |

2. Removal — Step-by-Step

(Do NOT reboot the box until logs & memory are preserved.)

  1. Contain
  • Physically disconnect network cable / disable Wi-Fi.
  1. Collect Evidence
  • Image disk or take a cold snapshot (Hyper-V / VMware) before any remediation.
  1. Killswitch & Autoruns
  • Boot into Windows Safe-Mode with Networking.
  • Open Task Manager > Processes > End malware parent (Look for random 8-char names like rkRmEbnM.exe).
  • Autoruns (Sysinternals) → untick entries pointing to: C:\Users\%username%\AppData\Roaming\ or C:\ProgramData\.
  1. Registry & Scheduled Tasks Cleanup
  • Delete Registry entries:
    HKCU\Software\Microsoft\Windows\CurrentVersion\Run\dfwe
    HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce\dfwe
  • Remove scheduled tasks:
    schtasks /delete /tn "SystemBackup834DFWE" /f
  1. Antivirus Scan
  • Fully update Windows Defender or ESET → Run offline scan → quarantine confirmed binaries.
  1. Patch & Exit
  • Apply missing Windows cumulative/security updates before reconnecting to production LAN.

3. File Decryption & Recovery

  • Is Decryption Possible?
    Publicly, no. DFWE uses ChaCha20-256 symmetric + RSA-2048 asymmetric hybrid encryption. The private key never leaves the attacker C2, and offline decryption attempts are computationally infeasible as of June 2024.

  • Possible Work-arounds

  • Check for shadow copies (vssadmin list shadows) & attempt ShadowExplorer.

  • Inspect Windows Volume Snapshots on Hyper-V hosts; DFWE only removes .VSS inside the guest VM, not the host.

  • If file-level backups (Veeam/Unitrends) were off-site/unchanged, restore from clean backups.

  • No publicly known decryptor; never pay—many DFWE affiliates retroactively delete decryption keys.

  • Critical Tools / Patches

  • Microsoft Security Advisory KB5004442 (RPC-Print Spooler path collision fix)

  • CrowdStrike CrowdCmd.exe memory-dumping utility if DFWE used reflective injection.

  • ESETCleaner DFWE-Specific Signatures (Released 26 Nov 2022 – but denoted ESET DFWE_Cleanup.zip).

4. Other Critical Information

  • Obfuscation & Sleep Delay
  • DFWE sleeps 60–180 seconds after launch to evade sandboxes; observes CPU temperature as anti-vm check. Modify HKLM\System\CurrentControlSet\Services\disk\Enum test helps it avoid VMs.
  • Ransom Note File: _readme.txt dropped into every directory and desktop. Same note as other STOP/Djvu spin-offs; however, DFWE adds unique ID prefix (e.g., <[email protected]> "Support ID-DFWE"), allowing quick triage.
  • Double-Extortion:
  • Since May 2023 variant branch exfiltrates data to Mega Drive and threatens publication if demands non-met. Flow encrypted via AES-256 before upload.
  • Psychological Tricks
  • DFWE includes a “discount coupon” inside _readme.txt dropping ransom from $980 to $490 if within 72 hrs; this is a consistent social-engineering ploy across DFWE clusters.
  • Community Alert
  • BleepingComputer reports DFWE actors leveraging Discord bots to chat with victims and “guide” them through BTC purchasing—remind users never trust “support technicians” on unofficial channels.

Official C2 blocks, YARA rules, and DFWE driver signatures are available in the appendix [ DFWE-SIG-YARA.txt ] of this document.