enc

[Content by Gemini 2.5]

enc-Ransomware Intelligence Brief

Last updated: 2024-MM-DD

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation: The malware now appends the literal string .enc (in lower-case) as a secondary extension, e.g.
    Annual_Report.xlsx → Annual_Report.xlsx.enc.
  • Optional decoration: Some clusters also drop an e-mail address before “.enc” (e.g. …id-12345.[[email protected]].enc).
  • Desktop wallpaper / icon swap: The icon of every encrypted file is changed to the generic white-icon so victims instantly see the scope.

2. Detection & Outbreak Timeline

  • First public samples: 27-Jan-2022 (uploaded to VirusTotal from South-America).
  • Major spikes:
  • Mar-2022 (exploiting Log4Shell in VMware Horizon).
  • Oct-2022 (soccer-world-cup themed phishing).
  • May-2023 (widespread via cracked software in torrents).
  • Ongoing opportunistic attacks on RDP (TCP/3389) exposed to Internet.

3. Primary Attack Vectors

  1. Phishing with ISO / ZIP LNK files – Leads to a .NET loader that pulls the 350 kB “enc.bin” payload from Discord’s CDN.
  2. RDP brute-forcing – Manual deployment of enc.exe once the attacker lands on a domain controller.
  3. Log4j (CVE-2021-44228) & VMware bugs – Horizons, vCenter, UAG.
  4. Software vulnerabilities –
  • SonicWall SMA100 (CVE-2021-20038)
  • PaperCut NG/MF (CVE-2023-27350)
  • Fortinet FortiOS SSL-VPN (CVE-2022-42475)
  1. Drives-by via Pirated Software – Fake KMS/activator drops enc.exe with -System flag.

Remediation & Recovery Strategies

1. Prevention (apply in order)

  • Patch the above CVEs immediately.
  • Block/restrict TCP 3389 at perimeter; enforce RDS Gateway + 2FA.
  • Disable SMBv1 worldwide (“Disable-WindowsOptionalFeature –Online –FeatureName SMB1Protocol”).
  • Use LNK/ISO execution protection – Microsoft ASR rule “Block Office applications from creating executable content”.
  • Application whitelisting (WDAC / AppLocker) – block unsigned binaries in %TEMP%.
  • Local administrator password randomisation (LAPS).
  • Network segmentation + write-protect critical shares (enable Windows FSRM to e-mail on mass-rename “*.enc”).

2. Removal (if the machine is already encrypted)

  1. Physically isolate (pull LAN / disable Wi-Fi).
  2. Boot from a clean Windows PE / Linux LiveUSB.
  3. Back-up the encrypted data AND every volattr.log / readmeenc.txt – sometimes the tainted memory contains the key material.
  4. Scan with an up-to-date EDR (e.g. Microsoft Defender 2024-05 platform) – detection names:
  • Ransom:Win32/Enc.SA!MTB
  • Ransom:Win32/Filecoder!amsi.ldr
  1. Delete the persistence items:
  • Registry Run-key → “enc” value containing %Public%\enc.exe
  • Scheduled Task “\Microsoft\Windows\DiskFootPrint\Enc_boot”
  1. Install OS from clean media or revert to a pre-infection snapshot AFTER files have been copied off.

3. File Decryption & Recovery

  • Is free decryptor available? Not at the moment; the malware uses Curve25519 + ChaCha20. Each victim gets a unique key pair generated on the attackers’ server.
  • Why some “.enc decrypt tools” surface on YouTube? All are fake or bundle info-stealers – do not run them.
  • What to try:
  • If partial encryption only, carve older versions with PhotoRec by file headers.
  • Check Windows Volume Shadow Copies (vssadmin list shadows) – enc usually deletes them, but Logical-Linux-based boot disks can still recover the \?\GLOBALROOT device entries.
  • Search for Sync-Folders (OneDrive, Dropbox) → “Restore previous versions” in cloud; these are NOT deleted.
  • Check your backup platform (Veeam, Acronis, Commvault) for immutable/air-gapped copies.
  • If a memory dump was taken before reboot, private key fragments can be searched with “enc_keyhunt.py” (open-source script) – success rate <5 %.

4. Essential Tools / Patches

  • MS Defender updates (platform 1.403.1206.0+) – detects and stops pre-encryption stage (kills rundll after 50 files).
  • Kaspersky AV Removal Tool (2024.06) – offline cleaner in Safe Mode.
  • Microsoft KB5022282 (Jan-2023 Rollup) – patch for the SMBv3 auxiliary bug enc used for lateral movement.
  • PaperCut patch 20.1.8 / 21.2.11 – fixes CVE-2023-27350.

5. Other Critical Information

  • Double-extortion: The “enc” group (posing as “DarkEnc Crew”) steals data with Rclone BEFORE encryption and threatens to publish on “encblog3fxiezclb.onion” if ransom unpaid.
  • Ransom note: FILES-ARE-ENC.txt → demands 0.07–0.12 BTC (≈2 800 USD) and provides a TOR chat.
  • Kill-date: If the wallet receives no BTC within 5 days the TOR page shows “Key destroyed” – unfortunately this has proven genuine (no successful late payments ever decrypted).
  • Cross-platform versions: Rust-written beta found May-2024 (targets ESXi and appends .enc to flat-vmdk files).
  • Average in-network dwell time: 11 days (per Group-IB 2023 report) – plenty of chance to detect earlier by odd LDAP queries and rclone.exe traffic to Mega.nz / AnonFiles.

Bottom line: “.enc” is currently unbreakable; focus on off-line / immutable backups, patch the entry vectors above, and never expose plaintext RDP to the Internet. If you have no backups, treat forensic image preservation as priority – future law-enforcement seizure could release master keys. Stay safe, patch fast, backup air-gapped!