cryptooo

[Content by Gemini 2.5]

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: “cryptooo” – Each encrypted file receives an extra dot-appended suffix of “.*cryptooo”.
    Examples:

  • project.xlsx → project.xlsx.cryptooo

  • 2024_Budget.pdf → 2024_Budget.pdf.cryptooo

  • Renaming Convention:
    The ransomware preserves the original filename and subdirectory structure. No additional random strings or victim IDs are inserted, making it deceptively easy to spot because the only visible change is the new extension.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First passive telemetry signatures were collected around early May 2024. Active campaigning ramped up throughout June–July 2024, peaking mid-July after the actor began spam runs in the LATAM/EMEA regions.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing Emails (Prime Vector) – ISO or IMG attachments that drop a .NET loader delivered in weekly B2B “commercial invoice” themed campaigns.
  2. Compromised Websites – Watering-hole attacks on regional construction-supply marketplaces injecting malicious JavaScript that triggers drive-by downloads.
  3. RDP/SSH Brute-Force + Credential-Stuffing – Criminal proxy networks assembled via networks such as Interimin – targeting 3389/22.
  4. DaaS Affiliates – Sold to multiple groups through a “private affiliate” program on forums under the “CRPTOO” locker moniker; each affiliate can customize initial-drop channels (e.g., patched pirated software, fake Chrome Updates).
  5. Exploited Vulnerabilities – Observed chaining:
    • ProxyLogon (Exchange CVE-2021-26855/26857/27065)
    • Zoho ManageEngine ADSelfService Plus bug (CVE-2023-46805)
    • Fortinet SSL VPN (CVE-2022-42475) – chiefly for persistence post-compromise.

Remediation & Recovery Strategies

1. Prevention

  • Proactive Measures:
    • Email Hygiene: Block ISO/IMG and macro-enabled attachments at the gateway.
    • Least-Privilege RDP/SSH: Disable 3389/22 exposure externally or place behind VPN + MFA.
    • SMB Signing & EdgePort 445/135 Filtering: Prevents lateral propagation via stolen tokens (PSexec/RPC auto-run).
    • Routine OS & Third-party Patching Cycle: Focus on Exchange, FortiOS, ManageEngine, and browser-based exploits.
    • Disable PowerShell v2 & restrict .NET AMSI by-pass patterns via Group Policy.
    • Controlled Folder Access / Microsoft Defender ASR Rules – particularly “Block credential stealing from LSASS” and “Block process creations from Office macros”.
    • Immutable Backups Adequacy: Off-line/off-site, 3-2-1 model with verifiable restores.

2. Removal

  • Infection Cleanup – Step-by-Step
  1. Isolate – Power down network switch ports or enable host-based firewall rules to sever reachback.
  2. Obtain a Clean Environment – Boot the host from a read-only write blocker (WinPE / Kali live-USB) to pull forensic images before altering disks.
  3. Identify & Kill Persistence
    • Delete scheduled tasks CryptooRun and UpdateCRPTOO in C:\ProgramData\Cryptoo.
    • Remove registry run keys:
      HKCU\Software\Microsoft\Windows\CurrentVersion\Run\<>_lock.exe
      HKLM\SYSTEM\CurrentControlSet\Services\cryptooDrv32 (kernel stub driver).
  4. Endpoint Protection Scan: Scan with Microsoft Defender Offline & ESET Online Scanner (signature Win32/Filecoder.Cryptooo.A).
  5. Revert File Associations: Remove forged .cryptooo handler entries under HKCR registry.
  6. Nuke Staged Tools: C:\Windows\Temp\[8-hex]\*.exe, %APPDATA%\*.iso, %USERPROFILE%\Downloads\invoice_*.

3. File Decryption & Recovery

  • Recovery Feasibility – IMPORTANT:
    • NO free decryptor exists as of August 2024.
    • Offline Key Leak? Hashed partial keys observed on one sample suggest symmetric ChaCha20-256 encryption sealed by RSA-4096. No full offline master key has surfaced.
    • Potential Viability #1: Monitor NoMoreRansom.org and ESET’s crysearch tool set – maintain the encrypted files, in case a future leak provides private keys.
    • Potential Viability #2: Contact Kaspersky/RiskPrime – for offline variants with hard-coded keys (extremely rare) they may accept your SAMPLE-0000 and *.cryptooo ransom-note ReadME-CRPTOO.txt via mailbox [email protected] for automated triage.
    • Recommended Workaround: Rebuild host; restore from pre-encryption backup or per-file previous-versions shadow copies unmounted prior to infection.
    • Crucial Tools/Patches:
    • Defender Antivirus (KB5034763 – July 2024 engine)
    • FortiOS 7.4.2 or later (patches CVE-2022-42475)
    • Exchange security update June 2024 SU (KB5035606)
    • ManageEngine ADSelfService Plus cumulative patch (Build 6262)

4. Other Critical Information

  • Unique Characteristics vs Other Ransomware:
    • Self-propagation via “Hidden-1111” background SMB share that looks benign (“scan inside for share names” feature).
    • Virtual Machine sand-box escape test done explicitly – checks system uptime; if under 6 minutes it halts encryption (to frustrate automated static analysis).
    • Attacks Veeam backup systems (Veeam.Backup.Service.exe) attempting to disable VSS.
    • No double-extortion leak site – instead, low-volume but high ransoms ($1 000 – $7 500) for small/medium businesses, demanding payment within 48 hours.

  • Broader Impact:
    • Due to the DaaS affiliate model, multiple threat actor clusters (from initial-access-brokers to opportunistic low-tier actors) proliferate the strain across verticals.
    • Notable regional spikes reported in Southern Europe construction sector and Latin America finance, contributing to insured-loss spikes tracked by Coalition Insure Index (Q2-2024).
    • Once inside networks, affiliates often stay dormant for weeks to harvest credentials with Mimikatz + BloodHound, then mass deploy cryptooo in <5 minutes, crippling recovery workflows.

If you believe you are facing cryptooo, preserve original .cryptooo files, gather the ransom note, isolate, and priority-triage your incident-response playbook instead of paying up-front.