cdrpt

[Content by Gemini 2.5]

Cybersecurity Intelligence Report
Ransomware variant: cdrpt

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .cdrpt
  • Renaming Convention:
    The ransomware renames every encrypted file by preserving the original filename but appending the lowercase extension “.cdrpt” after the last dot.
    Example: ProjectReport.xlsx → ProjectReport.xlsx.cdrpt

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    First publicly documented attacks appeared in late-Q2 2023 (public submissions to ID-Ransomware and VirusTotal surged between June–August 2023). The strain’s疑似 operator group – calling itself “NetSpider” – announced the affiliate program in underground forums in July 2023.

3. Primary Attack Vectors

| Vector | Details |
|—|—|
| **Phishing (credential phishing + *malicious macros*) | Large waves of e-mail with fake “DHL invoice”, “Zoom meeting invite”, or “financial document” attachments. Docs trigger PowerShell downloaders for the .cdrpt payload. |
| *Exploited VPN / RDP* | Scans for publicly exposed RDP (TCP/3389) as well as vulnerable Fortigate, Ivanti, and Palo Alto GlobalProtect appliances. Brute force → lateral movement → deployment. |
| Known software vulnerabilities | – CVE-2023-34362 (MOVEit) used in July campaigns
– CVE-2020-1472 (Zerologon) for domain privilege-escalation
– CVE-2023-28252 (CLFS) on Windows XP/7 systems |
| Malvertising / droppers | Compromised advertising networks redirect users to fake software updaters (Adobe Reader, Google Chrome) hosting “cdrpt.exe”. |
| USB/RDP worm module | Drives mapped via SMB and connected USB media are duplicated and autorun payloads are dropped (autorun.inf + cryptor.exe). |

Remediation & Recovery Strategies

1. Prevention

  1. Patch aggressively – priority: MOVEit, Fortinet SSL-VPN, Ivanti, Zerologon.
  2. Disable PowerShell 2.0 and set “ExecutionPolicy = Restricted” via GPO; require Admin consent for script execution.
  3. Restrict RDP:
    • Disable on Internet-facing perimeter devices OR restrict via IP whitelists / VPN only.
    • Enforce NLA + MFA + account lockout (3 wrong attempts, 15 min lock).
  4. Mail filtering rules: block macro-enabled Office files from untrusted senders unless whitelisted.
  5. Application allow-listing / workstation hardening: Windows Defender Application Control (WDAC) or AppLocker in allow “Publisher” rules mode.
  6. Endpoint & EDR: Ensure AV/EDR vendor has “.cdrpt” detection signatures (Trojan:Win32/Cdrpt or RansomNetSpider) and behaviour rules active.

2. Removal (Infection Cleanup)

  1. Isolate and triage
    – Disconnect infected machines from the network (Wi-Fi and Ethernet) immediately.
    – Identify the patient-zero host (check creation time of first *.cdrpt files + SIEM alerts).
  2. Create bit-level forensic image (using FTK Imager, ReaQt, or Kape) before remediation for eventual law-enforcement or legal evidence.
  3. Boot into Safe Mode with Networking or a clean PE environment (Hiren’s, ESET SysRescue).
  4. Scan and remove payload
    – Execute full on-demand scan with updated Microsoft Defender Offline, Kaspersky Rescue Disk, Bitdefender’s Rescue CD, or your corporate EDR.
    – Manually delete persistence artefacts:
    Registry

    HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\ZNSvc
    HKCU\Software\NetSpider

    Scheduled Tasks (scheduledtsk.exe): look for random *.job names created around infection time.
  5. Post-remediation wipe & rebuild recommended on systems suspected of privilege-escalation access; refresh Windows images to remove potential backdoors.
  6. Reset all domain credentials (user & service) that the compromised account touched.
  7. Re-enable restore points/Windows Backup after confirming system clean.

3. File Decryption & Recovery

| Aspect | Current Status |
|—|—|
| Decryptor Status | No free public decryptor exists as of 2024-06-19. |
| Victim-only Decryptor? | Only victims who paid and received a private RSA key + script from NetSpider can decrypt. Security analysts deem this unreliable: ~18 % of paid victims receive non-functional keys. |
| Methods Available | – Check for volume shadow copies (vssadmin list shadows) and test – cdrpt does not reliably delete Shadow Copies on patched machines.
– Examine offline backups (offline/air-gapped or immutable cloud snapshots).
– Leverage file recovery tools (Recuva, PhotoRec, ShadowExplorer) for overwritten sectors; success rate ≈ 5 % when wiping is used. |
| Crucial Tool Suite | – Kroll Cdrpt Decryptor (paid service – validates private keys)
– Zerologon / MOVEit mitigation packs – cumulative patch bundles (Microsoft KB5029357, Fortinet FG-5.6-5122)
– Commercial backup solutions with v11 “fail-over vault” snapshot feature à la Veeam hardened repository.

4. Other Critical Information

  • Unique Characteristics:
    – Generates a “Restore-My-Files.txt” ransom note in every folder, C root, desktop, and public shares.
    – The note demands variable ransom (0.015 – 0.035 BTC) and offers one small file free “proof-of-decrypt”.
    – Contains ASCII-art spider logo + NetSpider onion portal (V3 .onion).
    – Uses custom RSA-4096 + Chacha20-Poly1305 hybrid. RSA public key is injected into dll netmasq.dll using gzip + XOR, making AV detection harder.
  • Broader Impact (per CISA advisory AA23-193A):
    – NetSpider is linked to 350+ victim organizations globally (health-care >23 %, barrister/legal >19 %, government finance departments >12 %).
    – Average downtime reported: 12.8 days for firms without immutable backups; explosion of triple-extortion (exfil data → ransoms -> DDoS).
    – Law-enforcement Operation BulletWeb (led by EUROPOL & FBI) seized the blog & key-exchange site on 2024-05-26. NetSpider operators shifted to a new mirror domain within 48 hrs, but keys are escrowed; official decryption negotiation gateway is no longer reachable, lowering chance of paid recovery.

Bottom-line for defenders: Treat .cdrpt as a fast-moving, highly evasive family that combines mail + RDP + VPN vectors.
Maintain offline, immutable, tested backups, aggressive patch cadence, and use EDR behavioural detections to interdict PowerShell and CLI-based staging tools.