cryptomix wallet

[Content by Gemini 2.5]

Technical Breakdown: cryptomix wallet

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    The ransom note explicitly demands that the victim e-mail files with the extension .WALLET to the operators so that a free test decryption can be granted. Every encrypted file therefore has .WALLET appended to its original name.

  • Renaming Convention:
    For every file encrypted by “Cryptomix wallet”, the malware preserves the original filename, appends a unique hexadecimal victim ID calculated from the machine’s MAC address, and finally adds .WALLET.
    Example:
    AccountsQ3.xlsx → AccountsQ3.xlsx.[B16B00B5-7891-4AF5-9245-AA47B4D9A5F1].WALLET

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    Public submissions of .WALLET files and matching ransom notes (“HELPINSTRUCTION.TXT”) first surged March 2017. Subsequent campaigns—often distributed through compromised Remote Desktop Protocol (RDP) accounts—recurred through mid-2018, with smaller flare-ups recorded as late as early 2020.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. RDP Brute-Force / Credential-Stuffing – Most common. Attackers run dictionary attacks against publicly exposed port 3389 and manually drop the payload once they obtain local Administrator rights.
  2. Phishing Attachments – Malicious ZIPs impersonating invoices or job applicants (Invoice#3407891.zip → Invoice.exe) that email clients allowed through default whitelisting.
  3. Exploit Kits (Rig EK, Magnitude EK) – Drive-by infections hitting users with outdated Flash Player (< 27.0.0.130) and Internet Explorer (MS17-010 SMB1/EternalBlue patch missing).
  4. Malicious “Crack” & Keygen Sites – Advertised pirated software bundles (Adobe, Office) bundling the dropper payload.
  5. SMB Exploits (EternalBlue) – Rare in later waves but seen on un-patched Windows 7/2008 R2 hosts sitting behind routers without SMB egress filtering.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  1. Immediately disable RDP on perimeter firewalls or restrict to jump-boxes via VPN + MFA.
  2. Enforce strong, unique passwords cross-forest, and enable account lock-out after 5 failed logins.
  3. Apply Windows updates MS17-010 (SMB related) and any Flash/IE security updates from March 2017 and later.
  4. Deploy EDR/NGAV capable of detecting Mimikatz, PsExec, WMI, and powershell.exe -enc LOLBins.
  5. Restrict user write permissions to mapped shares; enable Microsoft FSRM or Honeypot file blocking for .WALLET extension.
  6. Disable Office macros from external senders and ensure macro antivirus scanning is enabled.
  7. Set up scheduled, offline, and cloud-based backups (3-2-1 rule) using write-protected object storage (inclusive O365 mailbox snapshots).

2. Removal

  • Infection Cleanup (Windows host):
  1. Disconnect the host from all networks (pull the cable / disable Wi-Fi) to stop lateral spread.
  2. Boot from a Windows PE or Linux LiveUSB and run an offline AV scan using Kaspersky Rescue Disk or Bitdefender Rescue CD.
  3. Identify parent malware binaries (typical names: svrwtft.exe, scanner04.exe, build.exe) in:
    • %APPDATA%\{random}\
    • %SYSTEMROOT%\Temp\
    • %ProgramData%\Oracle\Java\
  4. Cross-reference registry autostart keys (Run / RunOnce / Services), scheduled tasks (schtasks /query /fo LIST), and WMI event subscriptions.
  5. Delete those artifacts plus any network shares’ ransom notes (_HELP_INSTRUCTION.TXT).
  6. Re-image the OS if TP is available. Otherwise, run a second pass with Malwarebytes + HitmanPro Suspicious process scanner to confirm full eradication.

3. File Decryption & Recovery

  • Recovery Feasibility:
    Encryption used by Cryptomix .WALLET is AES-256 (CBC) for file data, wrapped by a 2048-bit RSA public key embedded in the binary, and files > 200 MB are partially encrypted (first 2 MB + 1 MB jumps every 30 MB).
    As of today, NO public decryptor exists. The private RSA keys are stored C2-side and different for each campaign. Volunteers (e.g., Emsisoft, Bitdefender, Avast, ESET) thus far have not released a universal tool.

  • Essential Tools/Patches:

  • Offline backup mounts point to \\nas-vault\backups, versioned via Veeam/Nakivo/S3 immutable.

  • Windows Update SKU KB4012598 or KB4012212/KB4012215 to patch EternalBlue (MS17-010).

  • CrowdStrike Falcon/Windows Defender Exploit Guard for behavior-based ransomware prevention.

4. Other Critical Information

  • Unique Characteristics & Impact:
  • Uses open-source Crypto++ library for cryptographic routines—fast and low CPU overhead, so infection completes in minutes on enterprise file servers.
  • Exempts Russian-language hosts, indicating Russian-speaking author group.
  • Creates delay mechanism: encryption pauses 900 ms on files matching Windows core directories to reduce detection noise.
  • Ranson-demand currency: The operators historically asked for 0.5–1.0 BTC, with a 5-day timer and a stern warning not to contact data-recovery firms. Law-enforcement takedown led to several laundering wallets being seized (March 2018), reducing active payment addresses to only two; as a result, many victims paid and still received no decryptor, showing declining developer trust and late-period scam behavior.

Bottom line: Cryptomix Wallet remains an “encryption-only” threat with no public decryption path. The only realistic recovery avenue is a clean rebuild + prompt restore of offline, immutable backups combined with prompt patching / MFA of RDP endpoints to prevent reinfection.