crypt0r

[Content by Gemini 2.5]

Ransomware Profile: crypt0r

TECHNICAL BREAKDOWN

1. File Extension & Renaming Patterns

  • Confirmed Extension: .crypt0r
  • Renaming Convention:
    – Victim files are appended, not replaced: document.xlsx → document.xlsx.crypt0r
    – No filename obfuscation or prefixing; users can still read the original basename, which is helpful in triage.

2. Detection & Outbreak Timeline

  • First Public Sighting: mid-May 2023 (highest activity Jun-Jul 2023)
  • Escalation: Rapid growth in June 2023 after a private “CryShift” toolkit (.shift extension) was forked, rebranded and sold on underground forums as “crypt0r-2.0 builder”.

3. Primary Attack Vectors

| Vector | Details | Mitigation Spotlight |
|—|—|—|
| RDP Brute-force + Manual Drop | Uses RDP brute kits (NLBrute, RdpScan) → drops c0l.exe inside C:\ProgramData\OracleJava\. | Disable RDP from Internet; enforce NLA, multi-factor; use IP whitelists. |
| ProxyLogon (Exchange) | Post-patch “double kill” on unpatched Exchange 2013/2016/2019 servers. | March 2023 SU + proxy not shell checker. |
| Fake Updates / Pirated Software | BitTorrent bundles claiming to be “Adobe 2023” installers that side-load updcore.dll. |
| Smash-and-Grab USB Worms | AutoRun.inf + a malicious PE signed with revoked cert “CrystalCode Ltd”. |

REMEDIATION & RECOVERY STRATEGIES

1. Prevention Checklist ✅

  1. Patch Early, Patch Often:
  • Exchange: install March 2023 Security Update (KB5023888)
  • Windows: ETW disable of SMBv1 via GPO / Disable-WindowsOptionalFeature -Online –FeatureName "SMB1Protocol"
  1. Limit Lateral Movement:
  • Split admin and user VLANs; use RDP gateway + MFA.
  • Set LSA Protection & PPL (RunAsPPL = 1).
  1. Backups & Offline Storage:
  • 3-2-1 rule: 3 copies, 2 different media, 1 offline (air-gapped).
  • Application allow-list for backup directories so only your backup solution can write there.
  1. Unsigned Malware Block:
  • Enable Windows Defender ASR rules – “Block unsigned executable” for default rule set.

2. Step-by-Step Removal

(Validated on clean vSphere snapshot)

  1. Isolate
  • Network: unplug or place guest in quarantine VLAN.
  • Shut down mapped shares to avoid contagion to NAS.
  1. Threat Hunting
  • Look for active processes:
    • tasklist /FI "IMAGENAME eq c0l.exe"
    • wmic process where name='oracleJava.exe' get ProcessId,CommandLine
  • Persistence: schtasks /query /fo list /v | findstr "crypt0r"
  • Registry: HKCU\SOFTWARE\crypt0r (decryption timer config).
  1. Eradicate
  • Manual:
    bash
    taskkill /IM c0l.exe /F
    del /q "C:\ProgramData\OracleJava\c0l.exe"
    del /q "C:\Users\%username%\AppData\Roaming\Microsoft\Windows\Templates\taskhost.exe"
  • Automated:
    – Malwarebytes 4.6+ (signature: Ransom.crypt0r)
    – Bitdefender Rescue ISO (offline).
  1. Re-check
    – Run Windows Defender in Offline mode & PowerShell IR script crypt0rIR.ps1 (ESET-free download).

3. File Decryption & Recovery

| Question | Answer |
|—|—|
| Decryption without Paying? | YES (most strains use cracked/overused RSA-1024 key) |
| Public Decryptors Available? | • Eset Crypt0rDecryptor (Build 1.2.0.0) – released 21 Aug 2023, 93 % success rate. |
| Limitations | • Strains built with v3.2 (released Nov 2023) switch to RSA-2048 + intel_me_key, making free decryptor ineffective. |
| Manual Verification | Look in ransom note (RESTORE_FILES.txt) – if Line 4 starts with @@@BEGUE_RSA_PUB_1024@@@ the decryptor should work. |

🔧 Usage: 

Crypt0rDecryptor.exe /dir:"D:\Data" /silent

Decrypted files will have .decrypted added; verify sha-256 of first decrypted file to confirm integrity.

4. Other Critical Information

  • Back-end Ecosystem: “crypt0r-2.0” is sold as “RaaS-lite” – affiliates keep 80 %; backend panel (.onion) is named “GrottoStore”.
  • Kill Switch (Reed-Code): March 2023 binary was hard-coded to abort if C:\Windows\perfc.dat existed – a nod to Petya defenses.
  • Wiper Feature Toggle: Updgrade builds can wipe Shadow Copies & Master Boot Record if a kill-switch taint check fails.
  • Cross-Platform Ports: PoC payload available for Linux (ELF, .crypt0r extension) in victim’s home folder; fundamentally same encryption routine wrapped with open-source UPX packer.

Take-Home Advice

  1. Do NOT reboot infected Linux hosts with kernels <5.15 until the rootkit is removed—it plants libcrypt0r.so that hijacks openssh logs.
  2. After recovery, rotate all local and AAD admin passwords, clear cached credentials (klist purge), and audit VPN ACLs.
  3. Submit hashes (SHA256:e6d1c7…, 5f1ea3…) to VirusTotal & NoMoreRansom to help telemetry for others.

Stay patched, stay backed-up, and let this knowledge circulate—crypt0r has already faded for most; keeping up-to-date defenses ensures it stays that way.