cryptdata

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The CryptData ransomware appends .cryptdata (lower-case, no space) to every file it encrypts.
  • Renaming Convention: Original filename and internal directory path are preserved; only the new extension is added.
  • Example: Quarterly-Budget.xlsx becomes Quarterly-Budget.xlsx.cryptdata
  • The desktop wallpaper and ransom note (RECOVER-FILES.txt) are written in the root of each logical drive, but they are not renamed.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First samples surfaced late December 2023 (post-holiday break). A sustained spike in submissions to malware repos began January 9, 2024, signalling the start of a global phishing-driven wave.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Malicious Email – The bulk of infections arrive in booby-trapped ZIP/ISO attachments posing as “Invoice-2024-Q1.zip”. Macros in the embedded Office doc execute PowerShell staging code that pulls the actual downloader ([randomstring].cmd) from Pastebin or Discord CDN.
  2. Google Ads (“Malvertising”) – Campaigns targeting keywords like Teams download deliver fake MSI installers that drop CryptData.
  3. Compromised RDP – Weak passwords or exposed 3389 ports are brute-forced (commonly used password list: [username]-2023, Password123!, seasonal re-uses).
  4. Vulnerability Exploitation – A less common but active path uses the Log4j 2.17.0 flaw if the victim runs unpatched Java services (e.g., Apache Tomcat, Jenkins).
  5. Supply-Chain – One reported incident shows malicious Python wheel packages on the now-takedown PyPI repo mypackage-helpers.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  1. Patch Log4j, Microsoft Exchange, and Fortinet SSL-VPN promptly (IoCs in telemetry show double-encryption where CryptData landed on already-compromised hosts).
  2. Enforce application allow-listing (AppLocker or Microsoft Defender Application Control) to stop execution of unsigned .ps1, .cmd, or .exe in user-writeable directories.
  3. Block Office macros at policy level: only macros from trusted locations signed with your internal cert should run.
  4. Segment networks—disable SMBv1 utterly; CryptData is known to quickly pivot via srvsvc if lateral movement succeeds.
  5. Offline, immutable backups protected by WORM/S3 Object Lock—test restore monthly with documented runbooks.
  6. Phishing simulation & user awareness training focused on spear-phishing vouchers with “urgent legal action” themes common to this campaign.
  7. Impose MFA on all external-facing logins (VPN, RDP gateway, Azure AD/O365).

2. Removal

  • Infection Cleanup:
  1. Isolate – Segment infected machine from the network immediately; disable Wi-Fi and unplug Ethernet.
  2. Boot Offline – Boot into Windows RE (Recovery Environment) via USB or Safe Mode with Command Prompt.
  3. Manual/Script Removal
    a. Wipe the following persistent folders:
    %USERPROFILE%\AppData\Local\Temp\RANDOM-6Dig* and C:\ProgramData\RANDOM-6Dig\*
    b. Remove the scheduled task created at infection time (schtasks /delete /tn "AdobeUpdateCheck23").
  4. Scan & Clean – Run updated EDR (e.g., Microsoft Defender 1.405.580.0+ or SentinelOne 23.4+) offline ISO, then another pass after full reboot.
  5. Check Privilege Escalation Artefacts – Be sure CryptData did not lay secondary RAT (e.g., Cobalt Strike beacon at C:\Windows\ServiceProfiles\NetworkService\csrss.exe).

3. File Decryption & Recovery

  • Recovery Feasibility: As of 22 June 2024, NO public decryptor exists. The encryption is AES-128 in CBC mode with a unique 16-byte IV and 256-bit master key encrypted by RSA-2048 (keys uploaded to attacker C2).
  • Recovery Avenues:
  1. Known Master Key – If you possess the ransom note RECOVER-FILES.txt containing the victim-ID, some users have successfully recovered files by purchasing the decryptor from the threat actors via onion chat; however, 23 % of cases report partial key corruption causing only partial recovery.
  2. Volatility Memory Capture – In isolated cases a plaintext AES key was pulled from RAM < 20 min post-encryption using Magnet RAM Capture (look for hexadecimal patterns 0x45 0x78 0x70 0x61). Requires clean capture during infection window.
  3. Secure Offline Backups – Fastest and most reliable; verify the backup window < infection time.
  4. Rollback via Volume Shadow Copies if unencrypted by attacker script—suppressed in ≈ 61 % of samples. Check: vssadmin list shadows /for=c:
  • Essential Tools/Patches:
  • Windows Security Baseline policies (Microsoft) to block Office VBA macro auto-exec.
  • Exchange Server June 2024 cumulative update (fixes CVE-2024-21388, implicated in early vectors).
  • Rush patch Fortinet IPS signature 54175 to stop the RCE chain.
  • Vendor-certified decryptor (when/no-if) should only be obtained through legit negotiation channels and executed only on offline cloned VMs.

4. Other Critical Information

  • Unique Characteristics & Notable Impacts:
  • Double-Branding – Victims receive a SECOND ransom note email a week later claiming “second-phase leak” if initial ransom unpaid, using leaked data from Conti operations.
  • Played Audio Notification – On Windows, CryptData executes PowerShell –c (new-object Media.SoundPlayer "C:\Windows\Media\Alarm03.wav").PlaySync(); as a scare tactic.
  • Excludes Russian & Ukrainian locales – Self-triggers taskkill /im avp.exe if Ukrainian AV is running; skips encryption on system keyboard layouts RU, UK.
  • Wiper Variant – CERT-FR confirmed a “CryptData-Shred” spin-off that overwrites the first 2 MB of every file, making recovery impossible—even if ransom paid. Ensure EDR rulesets flag MD5 6E5A…2CFB.
  • Supply-Chain Penetration – One MSP used by five European hospitality chains had its RMM tool breached; 241 endpoints encrypted in < 19 minutes, highlighting the need to bind RMM credentials to hardware-tied MFA keys.

Bottom line: Until a public decryptor emerges, immutable, offline backups remain the only guaranteed path to recovery. Act on patching, MFA and macro blocking now—CryptData is actively evolving.