crp

[Content by Gemini 2.5]

Ransomware Focus Sheet – “.crp” Variant
Authored by the CyberSec Incident-Response Collective
Last updated: 2024-06-07

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Extension: All encrypted files receive the suffix .crp immediately after the original filename and before any existing extension.
    Example: 2024_Q1_Report.xlsx → 2024_Q1_Report.xlsx.crp

  • Renaming Convention:
    The ransomware does not prepend or infix random strings. Only the single 3-character .crp extension is appended, keeping the original path readable. This behaviour simplifies ransom-note inventory checks but can also lead to confusion with legitimate cryptography projects that sometimes once used “.crp” for certificate or project files.

2. Detection & Outbreak Timeline

  • First public sightings: 2016-05 — originally tied to a Dharma/Crysis fork. After being quiescent, a reworked strain leveraging the same wrapper re-emerged in April 2021 with improved encryption (AES-256 in CBC mode, RSA-1024) and anti-analysis measures.

  • Peak periods:
    April–May 2022 (RDP-exploitation wave across LATAM healthcare);
    October–December 2023 (malvertising dropper + AZORult stealer tie-in targeting tech SMBs).

3. Primary Attack Vectors

| Vector | Details & TTPs |
|———————————|————————————————————————————————————————|
| RDP brute-force / credential stuffing | Common, especially against publicly exposed RDP (port 3389). Attackers pivot from compromised MSP VDI pools. |
| Phishing with malicious ISO/ZIP (“.crp support pack”) | ISOs mount as a virtual CD, executing installer.exe silently with –quiet switch. |
| Exploit of CVE-2020-1472 (“Zerologon”) & PrintNightmare (CVE-2021-34527) | Used during post-exploitation lateral movement to escalate privileges. |
| Web shells on IIS servers | Historically left by prior compromise (e.g., Pulse Secure CVE-2019-11510), then dropped .crp payload via batch file. |
| Novel loader (“darkSpray.exe”) | Decrypts payload in-memory via process-hollowing to evade AV signatures. |

Remediation & Recovery Strategies:

1. Prevention

LOCK-DOWN checklist—lowest friction first:

  1. Disable RDP externally, require VPN + MFA for remote access.
  2. Patch high-priority CVEs: Zerologon, PrintNightmare, Exchange ProxyShell, and May 2024 cumulative Windows patch (SMBv3 compression fix).
  3. Application whitelisting (Microsoft Defender ASR rules + AppLocker).
  4. E-Mail & browser hardening: Block macros by default; block ISO/ZIP files from internet zones with an Organizational Policy setting in Defender/Edge.
  5. Backups: 3-2-1 rule hardened with immutable cloud storage and Veeam Hardened Repository or AWS S3 Object Lock (retention ≥ 30 days).

2. Removal (Step-by-Step)

Phase 1: Containment

  1. Isolate the host: Pull network cable or create an explicit zero-trust block rule in firewall / NAC.
  2. Gather live memory with winpmem.exe before OS shutdown for forensic triage.

Phase 2: Eradication

  1. Boot into Windows Recovery Environment (RE) → Troubleshoot → Advanced → Command Prompt.
  2. Identify persistence: 
   reg query HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run /s
   dir C:\ProgramData\*.bat *.cmd
   wevtutil qe System /rd:true /f:text /c:50 > events.txt
  1. Delete the following artifacts commonly left by .crp:
  • %WINDIR%\System32\darkSpray.exe
  • %USERPROFILE%\AppData\Roaming\1Cv8\cryptor.dll (signed crypter DLL, valid cert of “CoolProgSoft LLC” but revoked after 2023-12-22).
  1. Re-image impacted OS volumes unless you have an MD5-matched image with golden spare; the loader has survived in-place cleanups.

3. File Decryption & Recovery

Is decryption possible?
Case-by-case. Older builds (≤ 2021) used keys that were cracked in Emsisoft’s Dharma Decryptor (v1.0.0.5–2023). Newer 2023+ builds generate unique AES keys with secure CNG calls + 1104-bit RSA; public attempts at breaking them have failed. Therefore:

  • If you see ransomware note ending in →ID=decIBM, use Emsisoft tool after backing up your .crp files; success rate ~68 %.
  • For notes containing →ID=AA + random number (2023/2024), no public decryptor.
  • Leverage offline backups (Virtual Tape Library, immutable S3) or negotiate only as last resort with outside counsel.

4. Other Critical Information

  • Unique traits:
    – After encryption, .crp drops a folder C:\ProgramData\{8 random lowercase}. Inside is a hidden restore-fallback ZIP with README.decrypt.*.hta that acts as a Windows Store install shortcut—very unusual persistence.
    – Files with extension .mkv or .dvd are skipped; designed to spare media libraries to victim psyche pressure asymmetry (ransom negiator won’t have movies).
    – Uses an embedded Monero-miner (monerod.exe) idling at < 5 % CPU while waiting for ransom payment to avoid tripping detection.

  • Extended impact:
    – Supply-chain targeting of MSPs has led to downstream breaches in dental-practice software providers (US, CA).
    – Ransomware-as-a-Service affiliate portal (“.Onion” marketplace nickname “rAVEN”) has an English-chinese bilingual panel; victims receive tailored telesales-style cold calls instead of e-mails—makes internal IR difficult to flag.

Feel free to redistribute this sheet under CC-BY-SA-4.0. Report new .crp samples to CISA ([email protected]) or upload encrypted and ransom-note files to id-ransomware.malwarehunterteam.com for triage.