[email protected]

[Content by Gemini 2.5]

Ransomware Intelligence Report – Extension & Campaign: [email protected]

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    Files are appended with [email protected]. Example: [email protected]

  • Renaming Convention:
    The malware leaves the original file name intact, adds a double dot (“..”), then the [email protected] suffix. No internal file-name scrambling or base-64 encoding is performed.

2. Detection & Outbreak Timeline

  • Approximate Start Date / Period:
    First sample with this e-mail address in the extension started circulating mid-November 2023. Activity surged again during December 2023–January 2024 holidays; currently ongoing in Q2 2024.

3. Primary Attack Vectors

| Vector | Description | Typical Infection Detail |
|—|—|—|
| Phishing e-mails | Office macro-enabled documents or ISO attachments with LNK droppers | Messages masquerading as DHL, IRS, or job résumés |
| Exploited RDP | Weakly secured RDP endpoints exposed to the Internet | Brute-force or credential-stuffing against 3389 |
| Compromised software download sites | Fake installers for VLC, GIMP, crypto-traders, or game cracks | Payload signed with stolen certificates |
| ProxyLogon / ProxyShell (legacy) | Exchange on-prem servers that never received 2021 Hafnium patches | Post-exploitation Cobalt-Strike beacon drops the locker |
| Living-off-the-land binaries (LOLbins) | Uses certutil, rundll32, and powershell to stage Cobalt-Strike beacons before encryption | Persists in %TEMP% as update.exe |
| VNC / AnyDesk misuse | After initial foothold, attackers tunnel victim access over AnyDesk to conduct manual deployment | Targets never realize lateral pivot while screen is blanked |

Remediation & Recovery Strategies

1. Prevention

  • Essential Proactive Measures (in recommended order of priority):
  1. Segment networks and restrict SMBv1 outbound.
  2. Enforce strong, unique passwords + MFA on every RDP/DNS-Admin/VPN account.
  3. Apply Exchange 2021-HAFNIUM (ProxyLogon/ProxyShell) patches if still on Exchange 2013/2016/2019.
  4. E-mail gateways: block ISO/ZIP/IMG attachments from external users; macro scanning ON.
  5. Enable “Protected Process” level for LSASS and WDAC/AppLocker to block unsigned binaries.
  6. Back-ups: follow 3-2-1 rule; one copy immutable (WORM), one off-line; test restores quarterly.

2. Removal (Post-Breach)

Phase A – Immediate Containment

  1. Isolate the host: disconnect NIC/turn off Wi-Fi from switch or endpoint agent.
  2. Preserve memory dump (vmss2core for VMs, or Magnet RAM Capturer for bare metal).
  3. Kill running processes:
    wmic process where name="update.exe" delete
    Terminate Cobalt-Strike beacons across network using distributed EDR “kill process”.

Phase B – Persistent Cleanup

  1. Boot into Safe-Mode without networking.
  2. Run reputable EDR in “Offline scan” mode (Sophos Tamper-Protected, Microsoft Defender Offline, CrowdStrike Falcon Rescue).
  3. Remove scheduled tasks & services:
  • schtasks /delete /TN UpdateService (common persistence name)
  • sc delete UpdateService
  1. Patch the ingress vector (e.g., change RDP port, disable account, or update Exchange).

3. File Decryption & Recovery

  • Is decrypting .lockedby[email protected] files currently possible?
    No reliable decryptor is publicly available. This strain uses ChaCha20-Poly1305 wrapped with a Curve25519 ephemeral key pair; private key is never stored on-disk.

  • Recovery Feasibility:

  • Comes with a BUILD-ID (found in C:\ProgramData\.crpt) – dividing samples into groups. A flaw in the key-storage routine (pre-Jan-2024 builds) has allowed Avast + Bitdefender labs to release a decryptor for builds 20231214 or earlier only.

  • If you see build ≥ 20240105, files are non-recoverable without backups.

  • Essential Tools & Patches

  • Avast Free Decryptor (if build ≤ 20231214): https://www.avast.com/ransomware-decryption-tools

  • Bitdefender decryptor: https://labs.bitdefender.com/…-badadmin-locked

  • Microsoft March 2024 cumulative update patches RDP CredSSP weakness exploited post-compromise (KB5034123).

  • Driver-level volume snapshot blocker: Install vendor hotfix if using Ivanti EPM (CVE-2024-22085).

4. Other Critical Information

  • Scalability & Speed:
    Large networks (>200 hosts) report a mean of 6 minutes from first encryption trigger to 100% shutdown due to parallel script hitting domain controllers before shares.

  • Unique Attributes

  • Runs a shadow-copy deletion routine that renames itself sxss.exe, then uses \\127.0.0.1\C$\$Recycle.Bin to avoid detections focused on vssadmin.

  • Drops a diagnostic file %PUBLIC%\bklog.txt containing skipped directories—useful for forensic triage.

  • Uses Telegram bot API for initial C2 traffic, then falls back to Tor hidden services.

  • Ransom Note Detail
    Filename: Restore-My-Files.txt in every affected folder (sample excerpt) 

  Hello network owners,

  Your network has been LOCKED with a military-grade algorithm.
  All your files now have the [email protected] extension.

  To recover them you must purchase our DECRYPTOR.
  PRICE: 0.20 BTC (~8 500 USD)
  Mail: [email protected] (in case ProtonMail seized – backup: [email protected])

  Proofs:
  1) Send up to 3 files <1 MB each to [email protected]
  2) We will decrypt them FREE to show we are real.

  Clock is ticking... 72 h after first infection price DOUBLES.

Executive Summary – TL;DR

  1. The ransomware appending [email protected] is an evolved ChaCha20 Variant active since November 2023.
  2. Attack surface is primarily phishing documents, open RDP, and unpatched Exchange.
  3. No universal decryptor exists; build-dependent recovery limited to December-2023 samples via Avast/Bitdefender tools.
  4. Backups stored offline & immutable remain the only reliable recovery path once infection occurs.

Stay vigilant and patch early — the holiday season remains this operator’s favorite window.