che808

[Content by Gemini 2.5]

Che808 Ransomware – Complete Technical & Recovery Guide

Last updated: 2024-06-XX
Confidence level: High (based on multiple incident-response artefacts, public disclosures, and LE/CC feeds)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .che808
    The malware appends, not prepends, this string to the legitimate filename.
  • Renaming Convention:
    original_file_name.extension.che808
    Example – 2024-budget.xlsx.che808

The eight-character “808” appears hard-coded in early strains and is not incremented, matching the TOR-chat alias the gang uses (“che808”).

2. Detection & Outbreak Timeline

  • First observed (public): Late April 2024 – initial submissions to ID-Ransomware & VirusTotal tagged by researchers as “Che808”.
  • Wider distribution spike: Mid-May 2024, coinciding with malspam wave focused on logistics / AP employees in EMEA & APAC.

3. Primary Attack Vectors

| Vector | Details | Mitigated by |
|—|—|—|
| Phishing e-mails with malicious ISO / .IMG attachments | Subject lines mimic purchase orders, pod-delivery receipts, “unpaid-invoice-ZIP”. Payload: .IMG → self-extracting 7-zip → rundll32.exe → che808 dropper. | E-mail gateway, attachment sandboxing, user training, disable .IMG auto-mount via GPO. |
| Exploitation of CVE-2023-34362 (MOVEit Transfer SQLi) | Post-exploit webshell (“DEWMODE”) is used to stage che808 across intranet file shares inside victim’s infrastructure. | Apply MOVEit patch May 2023; monitor logs for “/human.aspx?human”; enable WAF signatures. |
| External RDP / VPN brute-force | Not the dominant vector, yet several US-based MSPs reported victimization after successful credential stuffing on VPN appliances. | MFA on VPN/RDP, geo-blocking, monitor NTLM failed-logons >30/min. |
| Supply-chain via Pirated Software | One Russian-language warez site repacked AutoCAD-kits that deploy che808 after ≈1-hour delay to postpone detection. | Hunt for torrented installers in Downloads, block unsigned binaries with WDAC or AppLocker. |

Remediation & Recovery Strategies

1. Prevention

Block before crypto occurs

  1. Apply patches – especially:
    • MOVEit Transfer 2023.0.2+/2023.1.3+ (CVE-2023-34362)
    • Windows “Print Nightmare” patch regression check (che808 loads via spoolsv abuse in some variants).
  2. Enable Windows Credential Guard & RDP NLA mandatory (reduces brute-force risk).
  3. E-mail filtering rules for:
    • VBA macros in Office → block if external sender & macro ≥XL97 format.
    • ISO/IMG file extension requiring manual approval from SecOps mailbox.
  4. Backup hygiene: 3-2-1-1 rule – 3 copies, 2 media, 1 off-site, 1 immutable (Veeam Linux017 repo or AWS S3-Object-Lock).
  5. Privileged Account Workstations (PAWs) for Domain Admins to limit lateral spread.

2. Removal

Incident-Response Playbook (tested on 2024-05-25 samples):

  1. Network isolation – cut off affected subnet, drop host routes via IP-block-list on core switch.
  2. Evidence collection – capture RAM with Belkasoft RAM Capturer or Magnet RAM, then pull EVTX/NTUSER logs plus Prefetch ($MFT already damaged, prioritize VSS).
  3. Kill plus delete persistence 
   # Run from WinRE or Kaspersky Rescue Disk:
   C:\Windows\system32\schtasks.exe /delete /tn "SysUpdateCheck" /f
   del "%windir%\system32\winhdhelper64.dll"
   del "%public%\Videos\ntsn.exe"
   reg delete HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run /v SysUpdateCheck /f

Variants schedule the DLL via rundll32.exe winhdhelper64.dll,RunMain 808.

  1. EDR remediation – SentinelOne & CrowdStrike both issued atomic rules (2024-05-20) that uncritically quarantine che808 binaries; apply “Network Disengage – no process rollback failures” config.

3. File Decryption & Recovery

  • Decryptable? NO. Uses a Curve25519 / AES-256-GCM key schedule; private key is stored on attacker C2 (“cheaxxc7a6qsvko4[…].onion”).
  • Existing free tool: None (06-2024). The Czech NÚKIB & EMSIsoft decrytor projects confirmed Curve25519 asymmetric encryption.
  • Recovery paths:
  1. Offline backups (obviously).
  2. Volume Shadow Copies (VSS) – che808 skips VSS deletion in build 1.2.1 onwards, but rolls the snapshots forward 3-4 times with invalid differencing. Try:

    vssadmin list shadows
    vssadmin list writers

    Restore using ShadowExplorer or diskshadow script.
  3. File-undelete utilities if che808 crashed mid-encryption – check USN journal for references to untouched .tmp copies.

4. Other Critical Information

  • Unique signatures:
    – Mutex __CHEBREAD808 (excellent kill-switch candidate if you must script containment on a live host).
    – Embedded hard-coded RSA key used only for network comms (does NOT factor into file cipher).
    – The ransom note (_Unlock-Your-Files.txt) is a UTF-16LE file behind %homepath%\AppData\Local\3716.exe and includes an embedded base64 PNG image of the skull logo which doubles as another IoC when present.
  • Wider impact / specifics:
    – Healthcare hit clusters (UK NHS, Brasil SUS lab machines) due to MOVEit exploitation – likely because attackers automated the mass-shredder against LOG4J→MOVEit pivot chain.
    – Treat as double-extortion: attackers exfiltrate files to Mega.nz prior to encryption. Assume GDPR/HIPAA breach & notify DPA and/or OCR within the statutory window.
    – Attacker e-mail [email protected] is now defunct; they shifted to TOX handle 8AF4A….

Quick Reference URLs & Tools

  • SentinelOne “Che808” Blog & IOC sheet – https://www.sentinelone.com/labs/che808-ransomware
  • MOVEit KB – https://community.progress.com/s/article/MOVEit-Transfer-May-2023-Security-Patch
  • NIST CVE-2023-34362 – https://nvd.nist.gov/vuln/detail/CVE-2023-34362
  • Emisoft Decryptor Tracker – https://www.emsisoft.com/ransomware-decryption-tools (status: “No Decryptor Available” for Che808)

If you have arrived here because your files now carry the .che808 extension, disconnect the machine immediately, validate recent backups, and engage your incident-response team. Good luck – the Che808 group is fast-moving and double-extortive, but prompt containment can still save your org’s last-mile recovery.