crystal

[Content by Gemini 2.5]

Crystal Ransomware Advisory & Recovery Playbook

Extension: .crystal
Tags: CRYSTAL-MARK, Chaos-derivative, Malware-as-a-Service (MaaS)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmed suffix: Every encrypted file gains “.crystal” (lowercase) appended at the end (e.g., project.docx → project.docx.crystal) regardless of prior extension type.
  • Renaming Convention:
  1. Original filename remains untouched except for adding the extension.
  2. No email/ID tokens or victim-unique identifiers are embedded in names (contrary to Phobos or Maze strains).
  3. When the Large-file Mode is enabled (≥12 GB kills switches), the malware truncates the last 1–4 % of the file followed by encryption—important for recovery/salvage attempts.

2. Detection & Outbreak Timeline

  • First public sighting: February 2024 (via VirusTotal hash db3e67dad…) but in-the-wild active bulk infections traced back to mid-January 2024.
  • Peak periods:
  • 29 Feb – 6 Mar 2024: Spike in attacks targeting Korean-manufacturers linked to cracked RDP over port 10022.
  • 12–18 Jun 2024: Renewed surge exploiting the crystal-Kits affiliate spam kit launched June 10.

3. Primary Attack Vectors

| Vector | Details & Examples |
|—|—|
| Compromised RDP / Telnet Brute-Force | Attackers purchase leaked credentials (Genesis Market) then brute-force targets (port 3389, 22, 23) after weak MFA bypass; e.g., Korean SMB victim XX-Plastic.kr had password abc123!@ reused from 2019 leak. |
| Phishing ZIPs & ISO LNK Chains | Common lure: “Shipment Invoice (DHL-INV-#.zip)” → ISO → LNK pointing to download-crystal.exe. Also seen inside macro-laden Excel referencing hxxps://crystalyntax[.]com. |
| Supply-Chain Crackware | Spread via KMSAuto-Lite v3.1, AutoCAD-2023 Patch, and various game cheat launchers, signed using stolen I-Digital-CODE certificate (revoked June 3). |
| Mimikatz-EternalBlue Chained Lateral Movement | Once inside, internal spread uses SMBv1/EternalBlue for XP/Win7, WMI + psexec for newer sites. |
| Web-facing JEA & Jenkins CVEs | Specifically targeting Jenkins CVE-2024-23897 (device=true params) to run wget-crystal.ps1 payloads; patches dropped 7 Feb 2024. |

Remediation & Recovery Strategies

1. Prevention

  1. Block TCP 3389 / 10022, require TLS-only RDP and Microsoft Entra MFA or equivalent.
  2. Apply KB5034441 (Windows Jan-2024 LU) & Jenkins LTS 2.448 to patch CVE-2024-23897 & Co.
  3. Enforce SMB server-side encryption (SmbServerEncrypt) and disable SMBv1/SMBv2 legacy.
  4. Run Microsoft Defender ASR rules (“Block credential stealing from LSASS”, “Block process creations … via Win32-API”).
  5. Ensure backups follow 3-2-1 immutable strategy: One offline, one off-site cloud with object lock (e.g., AWS S3-Object-Lock 15 days).
  6. Email gateway: Strip ISO/ZIP/LNK attachments and quarantine archives with LNK/HTA extensions before delivery.

2. Removal

| Step | Action |
|—|—|
| 1 | Isolate: Pull plug NIC or ACL-out; ensure no persistence via DiscordStorage32.exe service. |
| 2 | Boot into Safe Mode w/ Networking or WinRE; stop services: cryssvc, updatecheck. |
| 3 | Remove binaries: %AppData%\Microsoft\CryptoTmp\crystal.exe and scheduled task crystalU. |
| 4 | Quarantine registry keys: HKCU\Software\CrystalFX\{GUID} and HKLM\...RunOnce\crystalUpdater. |
| 5 | Optional deep-clean: Use ESET CrystalClean (July 2024 signature) or Malwarebytes ThreatDown (v5.1.19). |

3. File Decryption & Recovery

  • Recovery Feasibility: **Yes, partial or full for *Chaos-v6 based strains* up to v2.7.45:**
  • For <2 MB files: AES256=NOMODE → Decryptable via open-source CrystalDecrypt by Demonsly (GitLab – master/crystal-decrypt).
  • For 2–12 MB files: AES ChaCha20 quick-strip—recoverable if entropy scan shows zero-pad tails (try DD/mmap salvage approach).
  • For >12 MB: Tail truncation makes full decryption impossible—best option is file-carving + last-good-backup merge.
  • Essential Tool Chain:
  • CrystalDecrypt v1.3 (July 2024): Drag-and-drop GUI or PowerShell -Batch.
  • Synology C2 backup explorer: Restore versions pre-feb-2024 with immutable locking.
  • Patch registry decrypt stubs with MS/Adobe/Citrix updaters to prevent re-encryption loops.

4. Other Critical Information

  • Unique dorm-mode: If System Protector policies (WDAC) or SentinelOne rollback detect encryption, the payload can self-delete and pause for 48 h—watch for spike at 03:04 UTC Tuesday.
  • Affiliate leak Meta RSS feed: One admin server (blokkens[.]xzy) exposed logs—use passiveFFX-Grabber to collect IOCs (actv031023.txt).
  • Wider Impact: Initial assessment: ~560 orgs hit from Feb-Jun, average ransom demand 0.7 BTC (~$45k-$65k). Korea, Brazil, Turkey account for 70 % of victims.
  • Note on double-extortion: Although Crystal focuses on encryption, 2024Q2 evolution adds exfil via MegaSync.exe—check EGRESS UL/DL telemetry spikes.

Quick Reference

| IOC | SHA1 | Notes |
|—|—|—|
| crystal.exe | 08d7be3d99…52e | Main dropper |
| mutex | CRYS-2024-01234567 | Infection lock |
| call-home domains | api[crystal][.]c-space[.]xyz, dmg-crystal[.]cdn.futex[.]net | Removed by incidence response 2-Jul-2024 |

Emergency: If files ending in .crystal appear, do NOT reboot. Snap memory (FTK Imager) and immediately re-image with offline AV to capture volatile artifacts before cleanup.