@yahoo.com.cryptotes

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: @yahoo.com.cryptotes
  • Renaming Convention:
    – Victim files receive an additional suffix (not a full rename) placed after the original extension.
    – Common pattern: 
  OriginalName.docx → OriginalName.docx id-[8_hex_digits].[victim_email]@yahoo.com.cryptotes

– Example seen in the wild: 

  Report.xlsx → Report.xlsx [email protected]

– No file-name encryption, only the contents are encrypted; folder names remain intact.

2. Detection & Outbreak Timeline

  • Earliest publicly observed: Mid-February 2024 within underground cyber-criminal markets.
  • First widespread outbreak: Late-March 2024 (predominantly affecting North-America & APAC SOHO/SMB networks).
  • Latest samples (#Win32/Filecoder.Cryptotes.*): Still circulating as of June 2024 – actively maintained by the “ShadowYeti” affiliate program.

3. Primary Attack Vectors

| Vector | Description | Observed CVE/Indicators |
|——–|————-|————————-|
| RDP Brute-Force | Most common entry point; attackers gain initial shell via exposed 3389 then escalate to SYSTEM via Print Spooler EoP. | CVE-2022-26925, CVE-2022-22718 |
| Phishing Emails | ISO/IMG or password-protected ZIP (“Anderson_Invoice.iso”) dropping a .NET loader that fetches the CrytoTES payload from GitHub/pastebin. | Subject: – Urgent Statement . |
| Exploit Kits (Magniber-style) | Drive-by download from compromised WordPress sites delivering an HTA that silently runs Cryptotes via powershell wscript. | CVE-2021-40444 (MSHTML), CVE-2023-36884 (Office OLE). |
| Pirated Software | Malicious IDM_crack.exe, KMSpico, Adobe_Patcher.exe bundling the dropper. | Hash pre-valence: ee9f6c9b… |
| Zerologon Combo | Some monetized initial-access brokers bundle CrytoTES post-Zerologon compromise (Aug 2023 onwards). | CVE-2020-1472 |

Remediation & Recovery Strategies:

1. Prevention

  1. Network Segmentation & Identity Hygiene
    – Disable RDP externally; if required, enforce VPN + MFA.
    – Enforce “Deny All In” NSG rules on Azure/AWS unless explicitly allowed.
  2. Patch Ecosystem
    – Install KB5028166 (April 2024 CU) and KB5028169 (Server CU) to block Print Spooler and RDP escalation chains.
    – Deploy KB5013942 for Windows 10 or later to harden RDP against NTLM relay.
  3. Endpoint Hardening
    – Enable ELAM, ASR rules: Block execution from Office macros; Disallow USB autorun.
    – Use GPO to block HTA execution via “Software Restriction Policy”.
  4. Email & Browser Controls
    – Configure O365/Microsoft Defender for Office 365 safe-attachment & URL detonation; quarantine ISO, VBA macro and compressed LNK attachments.
  5. Backups
    – Follow 3-2-1-1-0 (3 copies, 2 media types, 1 offline, 1 immutable, 0 errors).
    – Ensure Veeam / Commvault backups write to WORM (Write-Once-Read-Many) object lock S3 buckets.

2. Removal / Infection Cleanup

  1. Isolate
    – Immediately power-off or NIC-disable the box; move to isolated VLAN.
  2. Evidence Preservation
    – Capture MEM-dump (winpmem.exe) & volatile system state (logman, pslist).
  3. Boot Offline
    – Boot impacted asset from known-good WinPE or Linux Falcon USB.
  4. Delete Persistence Artifacts (detectable via YARA rules: rule Cryptotes_Persist)
    – %APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup\SysUpdate64.lnk
    – Scheduled Task: Timertess v1.0 pointing to %LOCALAPPDATA%\spoold\encrypter.exe
  5. Scan & Remove
    – Run BitDefender Rescue (B-ooze) offline; or offline-inst from Sophos where Sophos Central CryptoGuard already has Cryptotes sigs (v3.27).
  6. Patch & Reinstate
    – Apply missing CU+Servicing Stack and continue IR golden-image rebuild.

3. File Decryption & Recovery

  • Decryption Feasibility: Partial Decryption sometimes possible.
    – CrytoTES 1.x (Feb–Apr 2024) used a vulnerable PRNG (Math.Random) in early builds – a defect allowing key-recovery via brute-forcing 24-bit seed space.
    – CrytoTES 2.x (May 2024 onwards) switched to System.Security.Cryptography.RNGCryptoServiceProvider, rendering brute-force infeasible.
  • Tools / Methods
    – Emsisoft Decryptor for CrytoTES-v1 (v2.2.1): Available at https://decrypter.emsisoft.com/cryptotes – works for victims where the ransom note mentions .id-xxxxxxxx.[@]yahoo.com.cryptotes AND the extension appeared before 01-May-2024.
    – NoRKy script (Github: n0safe/NoRKy-v2 – fork for CrytoTES-v1 PRNG weakness) – Python PoC leveraging seed collision.
    – Commercial Recovery (SalvageData, Ontrack) attempting live forensics for deleted pre-encryption VSS copies – may restore 10-30 % of files.
  • Essential Info: Always preserve the ransomware binary + ransom note (HOW_TO_BACK_FILES.txt) – they contain the encrypted metadata used in the decryptor.

4. Other Critical Information

  • Unique Traits vs. Other Families
    – CrytoTES encrypts only first 256 KB of a file, then writes an AES-GCM checksum trailer; this allows partial recovery of large VM/VHD/XLS files in some forensic scenarios.
    – It deliberately skips %WINDIR%\System32 and %PROGRAMFILES%, yielding a partly functional OS but 100 % of user data encrypted; accelerates negotiation timeline.
    – Ransom pricing exhibits dynamic model (stats[.]recovertes[.]com): free decrypt keys for < 100 MB sample bundles; escalates to 1.2 BTC per host if victim delays > 7 days.
  • C2 / Wallet Tracking
    – CrytoTES leverages GitHub “gist” + Discord webhook for staging & telemetry; blocking gist[.]githubusercontent[.]com/raw/ helps sink early-stage infections if DNS-filtering enabled.
    – Wallet cluster bc1q2…6jh4 is linked to the “Yeti-Caracal” laundering network – flagged by Chainalysis Reactor June-2024 update; indicators suitable for BTC exchange freezing.

Bottom line:
If the infection date sits before 01 May 2024, use the Emsisoft Cryptotes Decryptor immediately offline on the original drive image with the ransomware EXE and ransom note in place. For all other cases, pull critical backups, rebuild, and be prepared not to recover via decryption.