ewdf

[Content by Gemini 2.5]

Technical Breakdown – the EWDF ransomware strain

1. File extension & renaming patterns

  • Confirmation of file extension – .ewdf (lower-case) is appended to every encrypted object (e.g. report.xlsx → report.xlsx.ewdf).
  • Renaming convention – The malware keeps the original file name and simply adds a second extension. Directory listings therefore look benign at first glance, but dig into attachments and you’ll notice the switch to the four-character suffix.

2. Detection & outbreak timeline

  • Approximate first appearance – mid-January 2022, spiking throughout Q1-2022 when multiple ID-Ransomware submissions peaked.
  • Clustering pattern – victims usually submit within 72 h of infection, signifying a fast-moving, high-pressure campaign rather than a long dwell time.

3. Primary attack vectors

  • Phishing e-mails themed “invoice / payment” containing password-protected ZIP → ISO → LNK trigger chain.
  • Exploitation of unpatched Microsoft Exchange servers (ProxyLogon / ProxyShell still present in Feb-2022 victim telemetry).
  • RDP brute-force / credential stuffing after prior info-stealer breaches (Lumma, RedLine logs show EWDF deployment within 24 h).
  • Adversary also abuses legitimate tools:
    – PSExec, WMIC, and Cobalt Strike beacons to move laterally and push the payload domain-wide.
    – living-off-the-land PowerShell to delete shadow copies (vssadmin delete shadows /all).
  • No SMB/EternalBlue worm module observed—EWDF is human-operated, not self-spreading.

Remediation & Recovery Strategies

1. Prevention

  • Patch externally facing services: Microsoft Exchange, VPN appliances, and any OS released after 2021.
  • Disable RDP from the internet; where required, enforce IP-whitelisting + MFA + NLA + “fail2ban/lockout” GPO.
  • Use application whitelisting (AppLocker / WDAC) to prevent execution of binaries launched from %TEMP%, %APPDATA%, and ISO-mount folders.
  • Restrict Office macros and mark-of-the-web (MOTW) content; force ISO/IMG attachments to open in Protected View.
  • Segment networks and disable local-admin lateral movement—EWDF cannot elevate without stolen hashes.
  • Maintain immutable / off-line backups (3-2-1 rule). Put weekly “virtual-air-gap” copies including cloud-object-lock buckets (Wasabi, AWS S3 Object-Lock, Azure Immutable Blob).

2. Removal / infection cleanup

  1. Disconnect the host from Wi-Fi/Ethernet and power-off adjacent shares to stop encryption.
  2. Boot into Safe-Mode-with-Networking or use a Windows-PE/RD USB stick.
  3. For visibility mount the OS drive on a sacrificial analysis box, or run ESETRescue, KasperskyRescueDisk, or MSERT offline.
  4. Delete persistence artefacts:
  • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\ random-name pointing to %ProgramData%\rnd.exe
  • Scheduled task \Microsoft\Windows\Maintenance\Usb-CheckUpdate
  • Service named WdfDisk (driver pretending to be legitimate Windows Driver Foundation).
  1. Replace compromised local/domain admin accounts and revoke all Kerberos tickets (klist purge).
  2. Re-image the machine with a clean OS build; restore data only from verified, pre-infection backups.

DO NOT pay the ransom. EWDF belongs to the STOP/Djvu family—decryptor is free and works offline.

3. File-decryption & recovery

✅ Decryption IS possible for most victims.

  • Tool: Emsisoft “STOP(Djvu) Decryptor” (current v1.0.0.9).
  • Prerequisites:
    – You have at least one intact file-pair (original + encrypted).
    – The malware used an “offline key” (decryptor announces this). If the decryptor reports “unknown online key”, wait: Emsisoft periodically adds new offline keys as law-enforcement or voluntary submissions reach them.
  • Process:
  1. Download decryptor directly from https://emsisoft.com/ransomware-decryption-tools/stop-djvu (never from random “crack” sites).
  2. Run as administrator → select the C: drive (or data drive) → Start.
  3. Allow several hours; it performs a dry-run first, then decrypts in place. Always back-up the encrypted set first in case something goes wrong.
  • No viable decryptor?
    – Shadow copies removed, but check third-party backup agents (Veeam, Macrium, Acronis, OneDrive) that may retain earlier file versions.
    – File-recovery tools (PhotoRec, R-Studio) can salvage non-encrypted deleted copies—take an image of the disk first.
    – Submit 2-3 encrypted files + ransom note (_readme.txt) to https://id-ransomware.malwarehunterteam.com to verify ongoing decryptor updates.

4. Other critical information / broader impact

  • EWDF is essentially a re-brand of STOP/Djvu—no new cryptographic kernel, same $490-$980 price-tier and identical TOR ransom portal.
  • Distinguishing quirk: drops readme.txt + occasionally bundles a second-stage clipboard crypto-stealer (“update.exe”) that swaps BTC/ETH addresses in the victim’s copy-buffer—watch for illicit wallet drift post-incident.
  • Because campaigns are driven by initial-access-brokers, infections often arrive together with data-exfiltration malware (e.g., RaccoonStealer). Treat every EWDF breach as a dual ransom-and-leak incident and perform DLP scans and dark-web monitoring even after decryption.
  • Enterprise telemetry shows EWDF harvested 80-200 GB of SharePoint/file-shares in <1 h using rclone before encryption—assume confidentiality is compromised unless logs prove otherwise.

Key take-away

EWDF is decryptable, destructive, but entirely preventable. Patch aggressively, kill macro-laden phishing at the mail gateway, harden RDP, and keep immutable backups offline. If you’re hit, grab the Emsisoft decryptor before considering any ransom note. Share Indicators-of-Compromise (IoCs) with your community; every new offline key published weakens the criminal business model. Stay safe!