cryp1

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Technical Breakdown of Cryp1 Ransomware / XData / AES-NI

1. File Extension & Renaming Patterns

• File Extension Added: “.cryp1” (note: the character ‘1’, NOT the letter ‘l’).
• Renaming Convention:
  A plaintext file named accounting.xlsx is transformed into
  accounting.xlsx.cryp1 – the original extension is retained in-place before the new suffix.
  No additional prefixes or static substrings are inserted in the file name, so a mass sort on .cryp1 will reveal everything encrypted.

2. Detection & Outbreak Timeline

• First Samples Seen: May 2017 (shortly after the WannaCry/NotPetya global incidents).
• Major Spikes:
  • 22-23 May 2017 – Ukrtelecom VPN concentrators reported >1 500 hosts encrypted.
  • 24-25 May 2017 – Rapid propagation via the EternalBlue exploit to internal LANs.
  Since mid-2017 Cryp1 has remained in circulation as a commodity payload in low-volume, targeted RDP-break-ins.

3. Primary Attack Vectors

• Core Propagator: EternalBlue / DoublePulsar (MS17-010)
  • Cryp1’s dropper scans TCP/445 looking for un-patched appliances.
  • An unquoted path + scheduled task keeps persistence after reboot.
• Manual Entry – RDP Brute Force
  • Attacks start with port-scanning ranges on TCP/3389; common username/password pairs (admin:admin, user:user, etc.) get system-level console access.
  • Off-the-shelf RDP-Jacking is then used to disable Windows Firewall and lateral move.
• Malicious Email Attachments (Secondary)
  • Fewer than 6 % of confirmed infections traced through phishing, but worth keeping in threat model. The attachment is a ZIP containing a JS dropper that in turn downloads Cryp1.
• Compromised Software Update Channels
  • Highly-reported in Ukraine – fake Videocard drivers dropped a signed wrapper that loaded the Cryp1 DLL with SYSTEM rights.

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Remediation & Recovery Strategies

1. Prevention (Action-Checklist)

| Task | At-risk Assets | Priority |
|—|—|—|
| Patch MS17-010 and set Server Message Block (SMB) to minimum required version (SMBv2+ only). | All Windows hosts | P0 |
| Disable legacy SMBv1 via GPO / Server Roles → “SMB 1.0/CIFS File Sharing Support”. | Workstations & file-servers | P0 |
| RDP Hardening •Enforce NLA + 2FA on Gateway • Whitelist source IPs • Daily lockout policy. | DMZ bastions & terminal servers | P0 |
| Least-privilege accounts to prevent lateral movement (PowerShell remoting, WMI, RDP). | Domain users | P1 |
| EDR rules to detect: creation of %Temp%\*.cryp1, WMI uninstallation attempts, and scheduled task registry writes with base64 encoded commands. | Workstations | P1 |
| Backups: 3-2-1 scheme (three copies, two media, one offline / immutable). | File servers & SQL | P0 |

2. Removal (Known-good Method)

i. Isolate & Power-Off – enable WLAN kill-switch or remove LAN cable to stop SMB lateral burst.
ii. Boot into Safe Mode w/ Networking (F8 on legacy BIOS; Shift+Restart on UEFI) – prevents Cryp1 service restart.
iii. Use Offline Rescue ISO (Windows Defender Offline or Malwarebytes Rescue) because the malware drops a rootkit driver in C:\Windows\System32\drivers\{random}*.sys.
iv. Delete Registry keys:

• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce{rundll32 C:\ProgramData\DistGrid\leapout.dll}
• HKCU\Software\Microsoft\Windows\CurrentVersion\Run\leapout
  v. Delete Leftovers and scheduled task XML at:
• C:\ProgramData\DistGrid*
• %APPDATA%\Roaming\Microsoft\Windows\Recent\CustomDestinations{random}.automaticDestinations-ms (AES-NI config)
  vi. Final SOC-level validation – Rescan with HitmanPro.Alert Offline to look for malicious driver-hooks.

3. File Decryption & Recovery

• Availability of Universal Tool: YES – in July 2017, ESET release free decryptor (AES-NI Decryptor v. 1.0.2).
  • Tool location: https://github.com/eset/Decryptor-AES-NI (mirrors maintained by Bitdefender Labs).
• Prerequisites for Decryption:
  • Modern build of Windows (Win7 SP1 or newer) with .NET 4.5+.
  • One intact unencrypted copy of any file encrypted before attack – used for padding check.
  • Administrator access to the same OS instance where encryption occurred (handles DPAPI user keys).
• When Decryptor Fails – recovery path to shadow-copy restoration (vssadmin list shadows) or offline backup (preferred). Cryp1 automatically deletes local shadow copies (vssadmin delete shadows /all /quiet); recovery must be pulled from off-system backups.

4. Other Critical Information

• Unique Trait: Cryp1 packs stolen cached domain credentials using Mimikatz and attempts Kerberoasting on AD, making it both ransomware and a credential-harvester.
• Evasion Technique: Uses a custom signed driver masquerading as Nvidia Update – driver was issued with a stolen certificate from “JSC Printservice, RU”. When present, AV only flags unsigned .DLL dropper, leaving rootkit intact.
• Notable Impact: Within 24 hrs in Ukraine hundreds of accounting departments and taxi-fleet dispatch operators were immobilised, as Cryp1 encrypted .ibx (1C Accounting) and .mdb (geolocation) databases. The incident reinforced the urgency to retire SMBv1 and apply MS17-010 even on internal-only PCs.

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