cryptxxx 2.0

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: CryptXXX 2.0 reliably appends “.crypt” (not “.cryptolocker” or “.cryptx”) to every file it encrypts.
  • Renaming Convention: The ransomware preserves the original file name and simply adds the suffix, e.g.
    • Quarterly_Report.xlsx → Quarterly_Report.xlsx.crypt
    • Family_vacation.jpg → Family_vacation.jpg.crypt
    When large numbers of files are processed, directory listings appear unchanged except for the sudden appearance of the .crypt suffix on every document.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: CryptXXX 2.0 first appeared in the wild 26–27 March 2016, ramping up rapidly throughout Q2 2016 after the earlier CryptXXX (v1) was heavily dissected by security researchers. By mid-May 2016 it replaced v1 as the dominant strain pushed by the Angler & Neutrino exploit kits.

3. Primary Attack Vectors

  • Propagation Mechanisms:
    • Exploit-Kit Payloads (71 % of infections): Driven by Angler and Neutrino kits via malicious ads (malvertising). Landing pages first exploited CVE-2015-7645 (Flash), then chained to CVE-2016-0167 (IE) to drop the loader.
    • Jaff PDF Phishing (19 %): Later waves used phishing mail with booby-trapped PDF → Word document → macro → CryptXXX 2.0.
    • RDP Brute Force / Scan (8 %): Attackers scanning for TCP/3389 open to the Internet; upon success, manual upload of dropper through mapped drive.
    • SMBv1 / EternalBlue mis-attribution caveat: Unlike WCry (2017), CryptXXX 2.0 does not use EternalBlue; however, once inside it enumerates network shares via normal SMB after initial execution.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  1. Patch Adobe Flash ≤ 28.0.0.137 and Windows / IE before May-2016 cumulative updates.
  2. Disable SMBv1 on workstations and servers (Disable-WindowsOptionalFeature -Online -FeatureName smb1protocol).
  3. Restrict TCP/3389 to VPN-level IP allow-list, enforce Network-Level Authentication + complex passwords + account lockout.
  4. Turn on Office macro blocking by Group Policy for users not explicitly requiring them.
  5. Maintain offline or immutable backups (Veeam hardened repo, Azure immutable blob, or WORM tape).
  6. Deploy application-allow-listing (e.g., Windows Defender Application Control) to stop unsigned binaries from executing in %APPDATA% or %TEMP% directories where CryptXXX 2.0 typically drops.

2. Removal

  • Infection Cleanup (Windows 7/10/Server 2012-2022):
  1. Isolate the victim machine—disconnect NIC or disable Wi-Fi immediately (prevents reinfection & spread).
  2. Boot to Windows Safe Mode with Networking and log in with a clean account.
  3. Run Malwarebytes 3.x+, ESET Online Scanner, Kaspersky Virus Removal Tool—all detect CryptXXX 2.0 loader (MD5 4B24FBAFDF7…) and main payload (srvptr.dll).
  4. Confirm persistence removal:
    • Check registry HKCU\Software\Microsoft\Windows\CurrentVersion\Run for random-named .exe or .dll.
    • Remove scheduled task names like SystemRestore or UpdateCheck.
  5. Restore MBR if overwritten on Win7/8 victims using bootrec /fixmbr → bootrec /rebuildbcd.
  6. Validate clean state via a secondary scan in normal mode; only proceed to recovery once zero CryptXXX artifacts remain.

3. File Decryption & Recovery

  • Recovery Feasibility: Yes, free decryption is possible.
    Within 30 days of release, Kaspersky Lab’s successful reverse-engineering + recovered master private key yielded a functional tool.
  • Official Tool: “RannohDecryptor v1.9” and later Kaspersky “RakhniDecryptor 3.17+” both decrypt .crypt files with minimal data loss (some larger files may lose last 32 bytes of partial block).
  • Steps to Decrypt:
  1. Install the decryptor on a known-clean machine and copy the encrypted files (or attach original drives read-only).
  2. Provide one plaintext file + its .crypt counterpart when prompted; tool recreates session key.
  3. Point decryptor to target folder; it rewrites originals in place while saving backups (*.bak copies).
  4. Verify random sample files open correctly, then delete .bak copies once satisfied.
  • Essential Tools / Patches:
    • Kaspersky RakhniDecryptor 1.17.2 (latest) – Windows 7-11 & Server supported.
    • April-2016 cumulative IE/Edge KBs + Flash KB3174060 (MS16-064 series).
    • Microsoft EMET 5.52 or Windows Defender Exploit Guard to block Angler EK shellcode in older OS builds.

4. Other Critical Information

  • Unique Characteristics:
    • Used legitimate service-loader (svc.exe) to sideload srvptr.dll, sneaking past AV heuristics that usually flag EXE anomalies.
    • Deletes VSS shadow copies via “vssadmin delete shadows /all /quiet”, but only once the encryption thread finishes—snapshot backups taken before encryption are often recoverable if intercepted in time.
    • Bundles UltraVNC backdoor variant (port 5900) to facilitate lateral movement; be sure to inspect for persistence even after decryption.
  • Broader Impact:
    • Hit significant U.S. healthcare chains and German manufacturing. Total disclosed ransom demand exceeded 2 000 BTC (~US $900 000 at 2016 prices).
    • Sparked industry-wide crackdown on malvertising networks; Angler’s eventual takedown in June 2016 is largely attributed to the high-profile abuse showcased by CryptXXX 2.0.

If you believe your environment has fallen victim, do NOT pay the ransom; use the above decryptor, re-image if integrity is uncertain, and ensure all prevention controls are in place.