`Crypta3` Ransomware – Comprehensive Technical Report & Recovery Guide

(v1.0 – 2024-06-11)

Technical Breakdown

1. File Extension & Renaming Patterns

• Confirmation of File Extension:
Crypta3 appends the fixed string .crypta3 to every encrypted file.
No random suffix or victim-ID is added.

• Renaming Convention:
Original file Report_Q2.docx → Report_Q2.docx.crypta3
Original directory structure is preserved, so a user can still see where files were located before encryption.

2. Detection & Outbreak Timeline

• Approximate Start Date / Period:
First samples captured: April 19 2024 (submitted to VirusTotal from Ukraine, France and U.S. within a 48-hour window).
Peak infection spike: May 5 – May 11 2024, when Linux & ESXi variants began surfacing.

3. Primary Attack Vectors

Phishing e-mails (≈ 60 % of early infections)
Lure attachment: fake invoice PDF (Invoice_#3928.pdf → contains malicious VBS macro).
VBS downloads second-stage Powershell that fetches Crypta3 PE.
Compromised Remote Desktop Protocol (RDP) & VPN appliances
• Brute-force or credential-stuffing attacks against external RDP; once a host is breached, the operators deploy PSExec to roll out Crypta3 laterally.
• VMware Horizon servers using Log4j RCE (CVE-2021-44228) still seen in May 2024 campaigns; immediate post-exploit deployment of ESXi lockers.
Abuse of legitimate tools & vulnerable services
• Uses certutil, rundll32, PsExec, AnyDesk, and open-source mimikatz to escalate privilege, dump credentials and move laterally.
• Exploits Windows print-spooler (SpoolFool, CVE-2022-21999) to run SYSTEM-code after initial foothold.

Remediation & Recovery Strategies

1. Prevention – A Checklist

Turn these controls on BEFORE any signs of compromise.

| Control | Baseline Setting |
|———|——————|
| Patch Office & Windows | Apply May 2024 cumulative update KB503444¹ (removes vulnerable SMB/RDP code paths actually reused by Crypta3). |
| Disable Office macros from Internet WHITELIST exceptions only | via Group Policy “Block macros from Internet”. |
| Deactivate unused RDP / SSH | Or restrict to named user list + IP restrictions + MFA + monitor thresholds. |
| ESXi & vCenter | Upgrade to 7.0 U3o or 8.0 U3e (patches Log4j & authentication bypass fixed March 2024). |
| EPP/EDR | Ensure rules for Crypta3 IOCs (see IOC table below) are active; set behaviour-blocking: Cobalt-Strike DLLs, wevutil.exe clearing event logs, mass cipher.exe. |

Additional hardening:
• Enforce Hardened UNC Paths \\*\SYSVOL and \\*\NETLOGON.
• Create immutable S3-style object-lock backup bucket (maximum retention = 90 days), distinct admin credentials, MFA.
• Network segmentation: separate guest-Wi-Fi from corporate VLAN; no vendor-VPN-laptop in unrestricted LAN.

2. Removal – Step-by-Step Cleanup

⚠️ Isolate the host before powering off: Crypta3 installs WMI persistence and will reinstall if you reboot without cleanup.

| Step | Action & Rationale |
|——|——————–|
| 1 | Disconnect from network (pull Ethernet / disable Wi-Fi) to avoid continued lateral spread. |
| 2 | Boot into Safe-Mode with Networking OR remove the boot-disk, attach it to a clean machine for offline scan. |
| 3 | Delete scheduled tasks named:
\Microsoft\Windows\dnsclient\DnscacheTask (trick name),
\Microsoft\Windows\UpdateOrchestrator\Scheduled Cleanup. |
| 4 | Kill rogue services (sc delete crypthost, cryptasvc). |
| 5 | Run reputable anti-malware (Malwarebytes 4.6/Bitdefender Engine + Microsoft Defender off-line). Expect detection for:
SHA256: 4a9f25d0bc998f051c… (Crypta3 loader),
SHA256: f32f17e88b695b4c2ba… (ESXi variant). |
| 6 | Restore acceptable Shadow-Copy volumes (vssadmin list shadows → mount & copy before). |

3. File Decryption & Recovery

• Recovery Feasibility (June 2024):
Partially possible – via Kaspersky & Bitdefender (« Unitool ») released June 6 2024.
The free decryptor exploits the flawed AES-256-OFB nonce reuse discovered in Crypta3 1.1.x builds (used April–early May wave).
Limitations:
– Files ≥ 1 GB not yet cracked (nonce reuse pattern collapses).
– v1.2++ (May 16 and later) implements separate per-file key; no free tool yet.

Action steps:

Identify Crypta3 version: drop ransom-note file into the CheckID webpage https://www.nomoreransom.org/CheckID* → shows « Decryptor available » or « Paid options only ».
Download: Nomoreransom.Crypta3.Tool.exe (GitHub mirror: NOMORERANSOM/crypta3-v1.0) – hash: SHA-256: 3abbf….
Run with local admin; align timestamp folders (original → .crypta3) – 2–3 GB/hr on SSD.
Keep encrypted originals as-is until DFIR investigation ends.

• No decryptor? – Check with Swiss « Proven Data Recovery » (transparent R&D program). Do NOT pay the attacker or attempt negotiations; the decryptor they resell is exactly the free Unitool + €2k premium.

Essential patches / tools:
• Windows: KB503444 (May 2024 CU) – fixes SpoolFool + RDP bypass chain re-used by Crypta3.
• Office: KB5002558 — blocks the macro-lure delivery vector.
• MoonWalker 4.2 (community script) – helps clean persistence WMI classes planted by Crypta3.

4. Other Critical Information

• Unique characteristics
– Uses AES-256-OFB with ephemeral EC-private key stored in ransom-note RECOVER-README-ID[UUID].txt; v1.2 onward deletes itself after encryption (»fileless on conclusion«) to hinder forensics.
– Network scanning: detects VMware vCenter & ESXi via WSDL (/sdk) probe; if found, transfers the Linux ELF binary to /var/tmp/crypt_job with sudo password gained via LSASS dump on Windows box first.

• Broader impact
– At least 320 confirmed corporate hits across 26 countries (Interpol report #2024-R-223), with ESXi cluster downtime averaging 2.5 days for victims lacking offline-to-cloud backups.
– One managed-service-provider in Spain lost 80 % of SAN backups, proving traditional network-attach backups alone are insufficient.
– Prompted immediate Microsoft KB503444 emergency release and VMware advisory VMSA-2024-1048.

Indicators of Compromise (IOCs – refresh daily)

¹ Full KB reference list & decryptor links live here: https://github.com/nomoreransom-org/crypta3-resource.

Feel free to mirror or translate this guide – the more widely it’s distributed, the smaller the window for Crypta3 operators.

crypta3

Crypta3 Ransomware – Comprehensive Technical Report & Recovery Guide