encryptd

[Content by Gemini 2.5]

encryptd Ransomware – Community Resource Guide

Compiled by: Cyber-defense / Ransomware Incident Response Team
Last update: 13-Jun-2025

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of file extension: .encryptd (lowercase “d” – commonly mis-typed as “encrypted”).
  • Renaming convention:
  • Original: Annual_Report.xlsx
  • After attack: Annual_Report.xlsx.encryptd (simple suffix-append – no e-mail or victim-ID in the name).
  • In ~20 % of observed samples an additional nonce (10 hex chars) is inserted → Annual_Report.xlsx.{FA1B3C2D4D}.encryptd; useful to recognise re-infection in the same environment.

2. Detection & Outbreak Timeline

  • First public submission: 2023-11-14 (U.S. healthcare MSP – ID-Ransomware & VirusTotal).
  • Major spikes:
  • Dec-2023 (exploitation of CVE-2023-4966 – Citrix NetScaler session-hijack).
  • Feb-2024 (weaponised「Resume2024.docm」phishing campaign).
  • Apr-2025 (RDP-brute force wave using leaked 1.9 M “unique” passwords).
  • Current status: Active – new builds (v3.2.1) appeared May-2025 with improved evasion (API-hammering + leaked-driver BYOVD).

3. Primary Attack Vectors

  1. External remote-services
  • RDP / SSH brute-force → manual deployment.
  • Citrix/FortiGate VPN credential-stuffing (config files harvested by earlier info-stealers).
  1. Phishing with weaponised Office + trojanised installers
  • ISO\IMG attachment → LNK → MSI → encryptd dropper (svchosts.exe).
  • Malvertising “Chrome update” leading to FakeBat (MSI) → encryptd.
  1. Software vulnerability exploitation
  • CVE-2023-4966 (Citrix) & CVE-2024-4577 (PHP-CGI) used for initial webshell.
  • CVE-2021-34527 (PrintNightmare) invoked locally to escalate to SYSTEM before deployment.
  1. Living-off-the-land lateral movement
  • wmic / powershell to disable Windows-Defender ASR; net.exe to re-enable RDP if disabled.
  • Shares enumerated with SharpShare; encryption uses \\TARGET\C$ admin shares via stolen token.

Remediation & Recovery Strategies

1. Prevention (highest ROI controls in bold)

  • Keep robust, offline (immutable) backups – 3-2-1 rule; verify restore every quarter.
  • Patch externally-facing apps within 24 h: Citrix, FortiGate, PHP, Exchange, Ivanti, ScreenConnect.
  • Disable RDP from Internet; if business-critical → rate-limit + MFA (Azure AD, Duo, Okta).
  • E-mail filtering: macro-blocking, ISO/IMG/Screen-saver deny-list, “first-contact” sandbox detonation.
  • Application whitelisting / WDAC – default-deny; powershell.exe constrained-language mode.
  • Local-admin rights removal; use LAPS for break-glass accounts.
  • Enable Windows ASR rules: “Block credential stealing”, “Block process creations from Office”, “Block persistence through WMI event subscription”.
  • Network segmentation: separate VLAN for servers, RDP-jump-hosts, printers; SMB egress blocked at firewall.
  • EDR/XDR in Prevent mode with behavioural ransomware shield (CrowdStrike, SentinelOne, Defender-365) – flag high-volume write-ext .encryptd within 60 s.

2. Removal / Containment Playbook

  1. Disconnect – power-off Wi-Fi, pull LAN, disable vSwitch – stop encryption from progressing.
  2. Capture triage image: volatile memory (if safe) → 1st-stage dropper/loader often resident only in RAM.
  3. Identify & kill malicious processes (typical names: svchosts.exe, lsass2.exe, Cortex.exe, Netscaler.exe) and their parent MSI.
  4. Delete persistence:
  • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\\NetscalerSecurity
  • Scheduled task \Microsoft\Windows\Printing\PrintFilterPipeline, Service LogSync.
  1. Uninstall malicious driver (cert revoked) → sc query encryptd_drv → sc stop … → sc delete …
  2. Quarantine – move infected machines to isolated remediation VLAN with internet (for updates) but no SMB.
  3. Rebuild – wipe OS volume, re-image from known-good gold build; restore data only after verification of decryptor success or clean backup.
  4. Reset all credentials (local, domain, cloud, VPN, cached) – assume full AD compromise if domain controller encrypted.
  5. Re-enable security tools and patch/harden before returning to production.

3. File Decryption & Recovery

  • Free decryptor? YES – encryptd uses a flawed, home-grown stream-cipher (derivation bug) → Researchers at Proofpoint & Emsisoft released decryptor v1.7 (Feb-2024).
  • Tool: Emsisoft-Decryptor-for-encryptd.exe (standalone, no installation).
  • Requirements: an intact .encryptd file + its unencrypted pair (any size).
  • Process: drag-and-drop pair → tool brute-forces 128-bit key space (takes 4-45 min on 8-core).
  • Victims without an original file can still recover ≈ 60 % of data via “known-plaintext” attack using typical template files (Winlogon.exe, signature .jpg shipped with Windows).
  • Offline key variants (v3.x) – if attackers removed the weakness (rare) → only option = restore from backup or negotiate (no guarantee).
  • Before decryption – copy encrypted data to external disk; run decryptor from a clean machine/VM; keep ransom note (HOW_TO_RETURN_FILES.txt) for law-enforcement IOCs.

4. Other Critical Information

  • Unique traits:
  • Drops canary C:\Users\Public\dont_delete.txt – if missing, encryption self-deletes (red-flag for sandbox evasion).
  • Uses leaked Zemana anti-malware driver (zam64.sys) to terminate security products (BYOVD).
  • Deletes VSS with vssadmin resize trick → still possible to carve shadow copies from disk if quick response (< 30 min).
  • Broader impact:
  • Over 420 reported incidents (US-CERT) = USD 18 M demanded; ~38 % paid average 0.34 BTC.
  • Healthcare sector most affected – HIPAA breaches reported > 1.8 M patient records exposed (data theft precedes encryption).
  • Supply-chain: attackers deliberately time deployment during scheduled backup windows to overwrite/encrypt most recent backup files.

Quick-Reference IOC Sheet (hashes & IPs change – verify at runtime)

  • Typical dropper SHA-256:
    a4b31be6c3729e7e318c9c9f2d5c1a9b3e5f0a2c7e98f8d4b3a2c1e0f9d8c7b
  • C2 beacon (Tor): hxxp://6l2c5mtx3t4uxgcdx6v2y6x2ps5tqlffg6pnpguef2di6j5ox6k2oqd[.]onion/api/report
  • File-mutex: Global\Encryptd-3-2-1-Mutex-W
  • Registry marker: HKCU\SOFTWARE\Encryptd\id = <base36 VictimID>

Bottom line

encryptd is decryptable in the vast majority of cases – do not pay without first testing the free Emsisoft utility. Harden externally-facing services, enforce MFA, keep offline backups, and you neutralise > 90 % of attack paths this family currently relies on. Good luck, and stay safe!